Organic light emitting diode and organic light emitting device including the same

ABSTRACT

An organic light emitting diode (OLED) including at least one emitting material layer (EML) disposed between two electrodes and comprising a first compound including a fused hetero aromatic ring with at least one nitrogen atom and a second compound of a boron-based compound and an organic light emitting device including the OLED is disclosed. The first compound and the second compound may be the same emitting material layer or adjacently disposed emitting material layers. The OLED can lower its driving voltage and improve its luminous efficiency using the first and second compounds with adjusting their energy levels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119(a) to KoreanPatent Application No. 10-2020-0149127, filed in the Republic of Koreaon Nov. 10, 2020, the entire contents of which are incorporated hereinby reference into the present application.

BACKGROUND Technical Field

The present disclosure relates to an organic light emitting diode, andmore specifically, to an organic light emitting diode having excellentluminous properties and an organic light emitting device having thediode.

Discussion of the Related Art

As display devices have become larger, there exists a need for a flatdisplay device with lower spacing occupation. Among the flat displaydevices, a display device using an organic light emitting diode (OLED)has come into the spotlight.

The OLED can be formed as a thin film having a thickness less than 2000Å and can be implement unidirectional or bidirectional images aselectrode configurations. Also, the OLED can be formed on a flexibletransparent substrate such as a plastic substrate so that OLED canimplement a flexible or foldable display with ease. In addition, theOLED has advantages over LCD (liquid crystal display device), forexample, the OLED can be driven at a lower voltage of 10 V or less andhas very high color purity.

In the OLED, when electrical charges are injected into an emittingmaterial layer between an electron injection electrode (i.e., cathode)and a hole injection electrode (i.e., anode), electrical charges arerecombined to form excitons, and then emit light as the recombinedexcitons are shifted to a stable ground state.

Fluorescent materials of the related art have shown low luminousefficiency because only the singlet excitons are involved in theluminescence process thereof. The phosphorescent materials in whichtriplet excitons as well as the singlet excitons are involved in theluminescence process have relatively high luminous efficiency comparedto the fluorescent material. However, the metal complex as therepresentative phosphorescent material has too short luminous lifespanto be applicable into commercial devices.

SUMMARY

Accordingly, embodiments of the present disclosure are directed to anOLED and an organic light emitting device including the OLED thatsubstantially obviates one or more of the problems due to thelimitations and disadvantages of the related art.

An aspect of the present disclosure is to provide an OLED that can lowerits driving voltage and enhance its luminous efficiency and color purityand an organic light emitting device including the diode.

Additional features and aspects will be set forth in the descriptionthat follows, and in part will be apparent from the description, or maybe learned by practice of the inventive concepts provided herein. Otherfeatures and aspects of the inventive concepts may be realized andattained by the structure particularly pointed out in the writtendescription, or derivable therefrom, and the claims hereof as well asthe appended drawings.

To achieve these and other aspects of the inventive concepts, asembodied and broadly described, an organic light emitting diodecomprises: a first electrode; a second electrode facing the firstelectrode; an emissive layer disposed between the first and secondelectrodes and including at least one emitting material layer, whereinthe at least one emitting material layer includes a first compound and asecond compound, and wherein the first compound has the followingstructure of Formula 1 and the second compound has the followingstructure of Formula 4:

-   -   wherein each of X₁ to X₈ is independently CR₁ or N, wherein one        of X₁ to X₄ is N and the rest of X₁ to X₄ is CR₁ and one of X₅        to X₈ is N and the rest of X₅ to X₈ is CR₁, and R₁ is selected        from the group consisting of protium, deuterium, tritium, a        halogen atom, an unsubstituted or substituted silyl group, an        unsubstituted or substituted C₁-C₂₀ alkyl group, an        unsubstituted or substituted C₁-C₂₀ alkyl amino group, an        unsubstituted or substituted C₆-C₃₀ aromatic group and an        unsubstituted or substituted C₃-C₃₀ hetero aromatic group,        wherein at least one of R₁ is an unsubstituted or substituted        C₁₀-C₃₀ hetero aromatic group having at least one nitrogen atom;

-   -   wherein each of R₂₁ to R₂₄ is independently selected from the        group consisting of protium, deuterium, tritium, boryl, amino,        an unsubstituted or substituted C₁-C₂₀ alkyl group, an        unsubstituted or substituted C₁-C₂₀ alkyl amino group, an        unsubstituted or substituted C₆-C₃₀ aromatic group and an        unsubstituted or substituted C₃-C₃₀ hetero aromatic group, or        adjacent two of R₂₁ to R₂₄ form an unsubstituted or substituted        fused ring having boron and nitrogen, or an unsubstituted or        substituted fused ring having sulfur; each of R₂₅ to R₂₈ is        independently selected from the group consisting of protium,        deuterium, tritium, boryl, an unsubstituted or substituted        C₁-C₂₀ alkyl group, an unsubstituted or substituted C₁-C₂₀ alkyl        amino group, an unsubstituted or substituted C₆-C₃₀ aromatic        group and an unsubstituted or substituted C₃-C₃₀ hetero aromatic        group. In an embodiment of the application, the second compound        has the following structure:

As an example, a Highest Occupied Molecular Orbital (HOMO) energy levelof the first compound and a HOMO energy level of the second compoundsatisfy the following relationship (1):

|HOMO^(FD)−HOMO^(DF)|<0.3 eV  (1).

-   -   wherein HOMO^(FD) is a HOMO energy level of the second compound        and HOMO^(DF) is a HOMO energy level of the first compound.

In one exemplary aspect, the at least one emitting material layer mayhave a mono-layered structure.

Alternatively, the at least one emitting material layer includes a firstemitting material layer disposed between the first and second electrodesand a second emitting material layer disposed between the firstelectrode and the first emitting material layer or between the firstemitting material layer and the second electrode, and wherein the firstemitting material layer includes the first compound and the secondemitting material layer includes the second compound.

Optionally, the at least one emitting material layer may furthercomprise a third emitting material layer disposed oppositely to thesecond emitting material layer with respect to the first emittingmaterial layer.

In another aspect, an organic light emitting device, such as an organiclight emitting display device or an organic light emitting luminescentdevice comprises a substrate and the OLED disposed over the substrate,as described above.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the inventive concepts asclaimed.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure, are incorporated in and constitute apart of this application, illustrate embodiments of the disclosure andtogether with the description serve to explain principles of thedisclosure.

FIG. 1 is a schematic circuit diagram of an organic light emittingdisplay device in accordance with the preset disclosure.

FIG. 2 is a schematic cross-sectional view illustrating an organic lightemitting display device in accordance with an exemplary aspect of thepresent disclosure.

FIG. 3 is a schematic cross-sectional view illustrating an OLED inaccordance with an exemplary aspect of the present disclosure.

FIG. 4 is a schematic diagram illustrating energy levels among luminousmaterials in an EML are adjusted so that charges are transferredeffectively to the second compound.

FIG. 5 is a schematic diagram illustrating HOMO energy levels amongluminous material in an EML are not adjusted so that holes are trappedat the second compound.

FIG. 6 is a schematic diagram illustrating both HOMO and LUMO energylevels among luminous material in an EML are not adjusted so that holesare trapped at the second compound and an exciplex are formed betweenthe first and second compounds.

FIG. 7 is a schematic diagram illustrating a luminous mechanism bysinglet and triplet energy levels among luminous materials in an EML inaccordance with one exemplary aspect of the present disclosure.

FIG. 8 is a schematic cross-sectional view illustrating an OLED inaccordance with another exemplary aspect of the present disclosure.

FIG. 9 is a schematic diagram illustrating energy levels among luminousmaterials in EMLs are adjusted so that holes are transferred to thesecond compound.

FIG. 10 is a schematic diagram illustrating a luminous mechanism bysinglet and triplet energy levels among luminous materials in EMLs inaccordance with another exemplary aspect of the present disclosure.

FIG. 11 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure.

FIG. 12 is a schematic diagram illustrating energy levels among luminousmaterials in EMLs are adjusted so that holes are transferred to thesecond compound.

FIG. 13 is a schematic diagram illustrating a luminous mechanism bysinglet and triplet energy levels among luminous materials in EMLs inaccordance with still another exemplary aspect of the presentdisclosure.

FIG. 14 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure.

FIG. 15 is a schematic cross-sectional view illustrating an organiclight emitting display device in accordance with another exemplaryaspect of the present disclosure.

FIG. 16 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure.

FIG. 17 is a schematic cross-sectional view illustrating an organiclight emitting display device in accordance with still another exemplaryaspect of the present disclosure.

FIG. 18 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure.

FIG. 19 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure.

FIG. 20 is a graph illustrating voltage (V)-current density (J)measurement of the OLEDs fabricated in Examples and ComparativeExamples.

FIG. 21 is a graph illustrating electroluminescence peak intensitymeasurement of the OLEDs fabricated in Examples and ComparativeExamples.

DETAILED DESCRIPTION

Reference and discussions will now be made below in detail to aspects,embodiments and examples of the disclosure, some examples of which areillustrated in the accompanying drawings.

The present disclosure relates to an organic light emitting diode (OLED)into which a first compound and a second compound having adjusted energylevels are applied in an identical EML or adjacently disposed EMLs andan organic light emitting device having the OLED. The OLED may beapplied into an organic light emitting device such as an organic lightemitting display device and an organic light emitting luminescentdevice. As an example, a display device applying the OLED will bedescribed.

FIG. 1 is a schematic circuit diagram of an organic light emittingdisplay device in accordance with the preset disclosure. As illustratedin FIG. 1, a gate line GL, a data line DL and power line PL, each ofwhich cross each other to define a pixel region P, in the organic lightemitting display device. A switching thin film transistor Ts, a drivingthin film transistor Td, a storage capacitor Cst and an organic lightemitting diode D are formed within the pixel region P. The pixel regionP may include a first pixel region P1, a second pixel region P2 and athird pixel region P3 (see, FIG. 15).

The switching thin film transistor Ts is connected to the gate line GLand the data line DL, and the driving thin film transistor Td and thestorage capacitor Cst are connected between the switching thin filmtransistor Ts and the power line PL. The organic light emitting diode Dis connected to the driving thin film transistor Td. When the switchingthin film transistor Ts is turned on by a gate signal applied into thegate line GL, a data signal applied into the data line DL is appliedinto a gate electrode of the driving thin film transistor Td and oneelectrode of the storage capacitor Cst through the switching thin filmtransistor Ts.

The driving thin film transistor Td is turned on by the data signalapplied into the gate electrode so that a current proportional to thedata signal is supplied from the power line PL to the organic lightemitting diode D through the driving thin film transistor Td. And then,the organic light emitting diode D emits light having a luminanceproportional to the current flowing through the driving thin filmtransistor Td. In this case, the storage capacitor Cst is charge with avoltage proportional to the data signal so that the voltage of the gateelectrode in the driving thin film transistor Td is kept constant duringone frame. Therefore, the organic light emitting display device candisplay a desired image.

FIG. 2 is a schematic cross-sectional view of an organic light emittingdisplay device 100 in accordance with an exemplary aspect of the presentdisclosure. All components of the organic light emitting device inaccordance with all aspects of the present disclosure are operativelycoupled and configured. As illustrated in FIG. 2, the organic lightemitting display device 100 includes a substrate 110, a thin-filmtransistor Tr on the substrate 110, and an organic light emitting diode(OLED) D over the substrate 110 and connected to the thin filmtransistor Tr.

The substrate 110 may include, but is not limited to, glass, thinflexible material and/or polymer plastics. For example, the flexiblematerial may be selected from the group, but is not limited to,polyimide (PI), polyethersulfone (PES), polyethylenenaphthalate (PEN),polyethylene terephthalate (PET), polycarbonate (PC) and combinationthereof. The substrate 110, over which the thin film transistor Tr andthe OLED D are arranged, form an array substrate.

A buffer layer 122 may be disposed over the substrate 110, and the thinfilm transistor Tr is disposed over the buffer layer 122. The bufferlayer 122 may be omitted.

A semiconductor layer 120 is disposed over the buffer layer 122. In oneexemplary aspect, the semiconductor layer 120 may include, but is notlimited to, oxide semiconductor materials. In this case, a light-shieldpattern may be disposed under the semiconductor layer 120, and thelight-shield pattern can prevent light from being incident toward thesemiconductor layer 120, and thereby, preventing the semiconductor layer120 from being deteriorated by the light. Alternatively, thesemiconductor layer 120 may include, but is not limited to,polycrystalline silicon. In this case, opposite edges of thesemiconductor layer 120 may be doped with impurities.

A gate insulating layer 124 formed of an insulating material is disposedon the semiconductor layer 120. The gate insulating layer 124 mayinclude, but is not limited to, an inorganic insulating material such assilicon oxide (SiO_(x)) or silicon nitride (SiN_(x)).

A gate electrode 130 made of a conductive material such as a metal isdisposed over the gate insulating layer 124 so as to correspond to acenter of the semiconductor layer 120. While the gate insulating layer124 is disposed over a whole area of the substrate 110 in FIG. 2, thegate insulating layer 124 may be patterned identically as the gateelectrode 130.

An interlayer insulating layer 132 formed of an insulating material isdisposed on the gate electrode 130 with covering over an entire surfaceof the substrate 110. The interlayer insulating layer 132 may include,but is not limited to, an inorganic insulating material such as siliconoxide (SiO_(x)) or silicon nitride (SiN_(x)), or an organic insulatingmaterial such as benzocyclobutene or photo-acryl.

The interlayer insulating layer 132 has first and second semiconductorlayer contact holes 134 and 136 that expose both sides of thesemiconductor layer 120. The first and second semiconductor layercontact holes 134 and 136 are disposed over opposite sides of the gateelectrode 130 with spacing apart from the gate electrode 130. The firstand second semiconductor layer contact holes 134 and 136 are formedwithin the gate insulating layer 124 in FIG. 2. Alternatively, the firstand second semiconductor layer contact holes 134 and 136 are formed onlywithin the interlayer insulating layer 132 when the gate insulatinglayer 124 is patterned identically as the gate electrode 130.

A source electrode 144 and a drain electrode 146, which are formed ofconductive material such as a metal, are disposed on the interlayerinsulating layer 132. The source electrode 144 and the drain electrode146 are spaced apart from each other with respect to the gate electrode130, and contact both sides of the semiconductor layer 120 through thefirst and second semiconductor layer contact holes 134 and 136,respectively.

The semiconductor layer 120, the gate electrode 130, the sourceelectrode 144 and the drain electrode 146 constitute the thin filmtransistor Tr, which acts as a driving element. The thin film transistorTr in FIG. 2 has a coplanar structure in which the gate electrode 130,the source electrode 144 and the drain electrode 146 are disposed overthe semiconductor layer 120. Alternatively, the thin film transistor Trmay have an inverted staggered structure in which a gate electrode isdisposed under a semiconductor layer and a source and drain electrodesare disposed over the semiconductor layer. In this case, thesemiconductor layer may comprise amorphous silicon.

A gate line GL and a data line DL, which cross each other to define apixel region P, and a switching element Ts, which is connected to thegate line GL and the data line DL, may be further formed in the pixelregion P of FIG. 1. The switching element Ts is connected to the thinfilm transistor Tr, which is a driving element. Besides, a power line PLis spaced apart in parallel from the gate line GL or the data line DL,and the thin film transistor Tr may further include a storage capacitorCst configured to constantly keep a voltage of the gate electrode forone frame.

In addition, the organic light emitting display device 100 may include acolor filter layer that comprises dyes or pigments for transmittingspecific wavelength light of light emitted from the OLED D. For example,the color filter layer can transmit light of specific wavelength such asred (R), green (G), blue (B) and/or white (W). Each of red, green, andblue color filter may be formed separately in each pixel region. In thiscase, the organic light emitting display device 100 can implementfull-color through the color filter.

For example, when the organic light emitting display device 100 is abottom-emission type, the color filter layer may be disposed on theinterlayer insulating layer 132 with corresponding to the OLED D.Alternatively, when the organic light emitting display device 100 is atop-emission type, the color filter layer may be disposed over the OLEDD, that is, a second electrode 230.

A passivation layer 150 is disposed on the source and drain electrodes144 and 146 over the whole substrate 110. The passivation layer 150 hasa flat top surface and a drain contact hole 152 that exposes the drainelectrode 146 of the thin film transistor Tr. While the drain contacthole 152 is disposed on the second semiconductor layer contact hole 136,it may be spaced apart from the second semiconductor layer contact hole136.

The OLED D includes a first electrode 210 that is disposed on thepassivation layer 150 and connected to the drain electrode 146 of thethin film transistor Tr. The OLED D further includes an emissive layer220 and a second electrode 230 each of which is disposed sequentially onthe first electrode 210.

The first electrode 210 is disposed in each pixel region. The firstelectrode 210 may be an anode and include a conductive material having arelatively high work function value. For example, the first electrode210 may include, but is not limited to, a transparent conductivematerial such as indium tin oxide (ITO), indium zinc oxide (IZO), indiumtin zinc oxide (ITZO), tin oxide (SnO), zinc oxide (ZnO), indium ceriumoxide (ICO), aluminum doped zinc oxide (AZO), and the like.

In one exemplary aspect, when the organic light emitting display device100 is a bottom-emission type, the first electrode 210 may have amono-layered structure of a transparent conductive material.Alternatively, when the organic light emitting display device 100 is atop-emission type, a reflective electrode or a reflective layer may bedisposed under the first electrode 210. For example, the reflectiveelectrode or the reflective layer may include, but are not limited to,silver (Ag) or aluminum-palladium-copper (APC) alloy. In the OLED D ofthe top-emission type, the first electrode 210 may have a triple-layeredstructure of ITO/Ag/ITO or ITO/APC/ITO. In addition, a bank layer 160 isdisposed on the passivation layer 150 in order to cover edges of thefirst electrode 210. The bank layer 160 exposes a center of the firstelectrode 210.

An emissive layer 220 is disposed on the first electrode 210. In oneexemplary aspect, the emissive layer 220 may have a mono-layeredstructure of an emitting material layer (EML). Alternatively, theemissive layer 220 may have a multiple-layered structure of a holeinjection layer (HIL), a hole transport layer (HTL), an electronblocking layer (EBL), an EML, a hole blocking layer (HBL), an electrontransport layer (ETL) and/or an electron injection layer (EIL) (see,FIGS. 3, 8, 11 and 14). In one aspect, the emissive layer 220 may haveone emitting part. Alternatively, the emissive layer 220 may havemultiple emitting parts to form a tandem structure.

The second electrode 230 is disposed over the substrate 110 above whichthe emissive layer 220 is disposed. The second electrode 230 may bedisposed over a whole display area and may include a conductive materialwith a relatively low work function value compared to the firstelectrode 210. The second electrode 230 may be a cathode. For example,the second electrode 230 may include, but is not limited to, aluminum(Al), magnesium (Mg), calcium (Ca), silver (Ag), alloy thereof orcombination thereof such as aluminum-magnesium alloy (Al—Mg). When theorganic light emitting display device 100 is a top-emission type, thesecond electrode 230 is thin so as to have light-transmissive(semi-transmissive) property.

In addition, an encapsulation film 170 may be disposed over the secondelectrode 230 in order to prevent outer moisture from penetrating intothe OLED D. The encapsulation film 170 may have, but is not limited to,a laminated structure of a first inorganic insulating film 172, anorganic insulating film 174 and a second inorganic insulating film 176.

Moreover, the organic light emitting display device 100 may have apolarizer in order to decrease external light reflection. For example,the polarizer may be a circular polarizer. When the organic lightemitting display device 100 is a bottom-emission type, the polarizer maybe disposed under the substrate 110. Alternatively, when the organiclight emitting display device 100 is a top-emission type, the polarizermay be disposed over the encapsulation film 170. In addition, a coverwindow may be attached to the encapsulation film 170 or the polarizer.In this case, the substrate 110 and the cover window may have a flexibleproperty, thus the organic light emitting display device 100 may be aflexible display device.

Now, we will describe the OLED in more detail. FIG. 3 is a schematiccross-sectional view illustrating an OLED in accordance with anexemplary aspect of the present disclosure. As illustrated in FIG. 3,the OLED D1 comprises first and second electrodes 210 and 230 facingeach other, and an emissive layer 220 having single emitting partdisposed between the first and second electrodes 210 and 230. Theorganic light emitting display device 100 includes a red pixel region, agreen pixel region and a blue pixel region, and the OLED D1 may bedisposed in the blue pixel region. The emissive layer 220 comprises anEML 240 disposed between the first and second electrodes 210 and 230.Also, the emissive layer 220 may comprise at least one of an HTL 260disposed between the first electrode 210 and the EML 240 and an ETL 270disposed between the second electrode 230 and the EML 240. In addition,the emissive layer 220 may further comprise at least one of an HIL 250disposed between the first electrode 210 and the HTL 260 and an EIL 280disposed between the second electrode 230 and the ETL 270.Alternatively, the emissive layer 220 may further comprise a firstexciton blocking layer, i.e. an EBL 265 disposed between the HTL 260 andthe EML 240 and/or a second exciton blocking layer, i.e. a HBL 275disposed between the EML 240 and the ETL 270.

The first electrode 210 may be an anode that provides a hole into theEML 240. The first electrode 210 may include, but is not limited to, aconductive material having a relatively high work function value, forexample, a transparent conductive oxide (TCO). In an exemplary aspect,the first electrode 210 may include, but is not limited to, ITO, IZO,ITZO, SnO, ZnO, ICO, AZO, and the like.

The second electrode 230 may be a cathode that provides an electron intothe EML 240. The second electrode 230 may include, but is not limitedto, a conductive material having a relatively low work function values,i.e., a highly reflective material such as Al, Mg, Ca, Ag, alloythereof, combination thereof, and the like.

The EML 240 may comprise a first compound (Compound 1) DF, a secondcompound (Compound 2) FD and, optionally a third compound (Compound 3)H. For example, the first compound DF may be delayed fluorescentmaterial, the second compound FD may be fluorescent material, and thethird compound H may be host.

When holes and electrons meet each other to form excitons in the EML240, singlet exciton with a paired spin state and triplet exciton withan unpaired spin state is generated in a ratio of 1:3 in theory. Sincethe conventional fluorescent materials can utilize only the singletexcitons, they exhibit low luminous efficiency. The phosphorescentmaterials can utilize the triplet excitons as well as the singletexcitons, while they show too short luminous lifespan to be applicableto commercial devices.

The first compound DF may be delayed fluorescent material havingthermally activated delayed fluorescence (TADF) properties that cansolve the problems accompanied by the conventional art fluorescentand/or phosphorescent materials. The delayed fluorescent material hasvery narrow energy level bandgap ΔE_(ST) ^(DF) between a singlet energylevel S₁ ^(DF) and a triplet energy level T₁ ^(DF) (see, FIG. 7).Accordingly, the excitons of singlet energy level S₁ ^(DF) as well asthe excitons of triplet energy level T₁ ^(DF) in the first compound DFof the delayed fluorescent material can be transferred to anintermediate energy level state, i.e. ICT (intramolecular chargetransfer) state (S₁ ^(DF)→ICT←T₁ ^(DF)), and then the intermediate stateexcitons can be shifted to a ground state (ICT→S₀ ^(DF)).

Since the delayed fluorescent material has the electron acceptor moietyspacing apart from the electron donor moiety within the molecule, itexists as a polarized state having a large dipole moment within themolecule. As interaction between highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital (LUMO) in the delayedfluorescent material becomes little in the state where the dipole momentis polarized, the triplet excitons as well as the singlet excitons canbe converted to ICT state.

The delayed fluorescent material must has an energy level bandgapΔE_(ST) ^(DF) equal to or less than about 0.3 eV, for example, fromabout 0.05 to about 0.3 eV, between the singlet energy level S₁ ^(DF)and the triplet energy level T₁ ^(DF) so that exciton energy in both thesinglet energy level S₁ ^(DF) and the triplet energy level T₁ ^(DF) canbe transferred to the ICT state. The material having little energy levelbandgap ΔE_(ST) ^(DF) between the singlet energy level S₁ ^(DF) and thetriplet energy level T₁ ^(DF) can exhibit common fluorescence with Intersystem Crossing (ISC) in which the excitons of singlet energy level S₁^(DF) can be shifted to its ground state S₀ ^(DF), as well as delayedfluorescence with Reverse Inter System Crossing (RISC) in which theexcitons of triplet energy level T₁ ^(DF) can be converted upwardly tothe excitons of singlet energy level S₁ ^(DF), and then the exciton ofsinglet energy level S₁ ^(DF) transferred from the triplet energy levelT₁ ^(DF) can be transferred to the ground state S₀ ^(DF). In otherwords, 25% excitons at the singlet energy level S₁ ^(DF) and 75%excitons at the triplet energy level T₁ ^(DF) of the first compound DFof the delayed fluorescent materials are converted to ICT state, andthen the converted excitons are shifted to the ground state S₀ ^(DF)with luminescence. Therefore, the delayed fluorescent material may have100% internal quantum efficiency in theory.

The first compound DF may be delayed fluorescent material that includesan electron acceptor moiety consisting of a fused hetero aromatic ringwith plural nitrogen atoms as a nuclear atom, and an electron donormoiety consisting of a fused hetero aromatic ring with at least onenitrogen atom as a nuclear atom. The first compound DF of the delayedfluorescent material may have the following structure of Formula 1:

In Formula 1, each of X₁ to X₈ is independently CR₁ or N, wherein one ofX₁ to X₄ is N and the rest of X₁ to X₄ is CR₁ and one of X₅ to X₈ is Nand the rest of X₅ to X₈ is CR₁, and R₁ is selected from the groupconsisting of protium, deuterium, tritium, a halogen atom, anunsubstituted or substituted silyl group, an unsubstituted orsubstituted C₁-C₂₀ alkyl group, an unsubstituted or substituted C₁-C₂₀alkyl amino group, an unsubstituted or substituted C₆-C₃₀ aromatic groupand an unsubstituted or substituted C₃-C₃₀ hetero aromatic group,wherein at least one of R₁ is an unsubstituted or substituted C₁₀-C₃₀hetero aromatic group having at least one nitrogen atom.

For example, each of the C₆-C₃₀ aromatic group and the C₃-C₃₀ heteroaromatic group may be independently unsubstituted or substituted with atleast one of a C₁-C₁₀ alkyl group, a C₆-C₃₀ aryl group and a C₃-C₃₀hetero aryl group.

As an example, the C₆-C₃₀ aromatic group, which can be constitute R₁ inFormula 1, may comprise independently, but is not limited to, be aC₆-C₃₀ aryl group, a C₇-C₃₀ aryl alkyl group, a C₆-C₃₀ aryl oxy groupand a C₆-C₃₀ aryl amino group. Alternatively, the C₃-C₃₀ hetero aromaticgroup, which can be constitute R₁, may comprise independently, but isnot limited to, a C₃-C₃₀ hetero aryl group, a C₄-C₃₀ hetero aryl alkylgroup, a C₃-C₃₀ hetero aryl oxy group and a C₃-C₃₀ hetero aryl aminogroup.

For example, the C₆-C₃₀ aryl group, which can constitute R₁, maycomprise independently, but is not limited to, a non-fused or fused arylgroup such as phenyl, biphenyl, terphenyl, naphthyl, anthracenyl,pentalenyl, indenyl, indeno-indenyl, heptalenyl, biphenylenyl,indacenyl, phenalenyl, phenanthrenyl, benzo-phenanthrenyl,dibenzo-phenanthrenyl, azulenyl, pyrenyl, fluoranthenyl, triphenylenyl,chrysenyl, tetraphenylenyl, tetracenyl, pleiadenyl, picenyl,pentaphenylenyl, pentacenyl, fluorenyl, indeno-fluorenyl andspiro-fluorenyl.

Alternatively, the C₃-C₃₀ hetero aryl group, which can constitute R₁ maycomprise independently, but is not limited to, an unfused or fusedhetero aryl group such as pyrrolyl, pyridinyl, pyrimidinyl, pyrazinyl,pyridazinyl, triazinyl, tetrazinyl, imidazolyl, pyrazolyl, indolyl,iso-indolyl, indazolyl, indolizinyl, pyrrolizinyl, carbazolyl,benzo-carbazolyl, dibenzo-carbazolyl, indolo-carbazolyl,indeno-carbazolyl, benzo-furo-carbazolyl, benzo-thieno-carbazolyl,carbolinyl, quinolinyl, iso-quinolinyl, phthalazinyl, quinoxalinyl,cinnolinyl, quinazolinyl, quinolizinyl, purinyl, benzo-quinolinyl,benzo-iso-quinolinyl, benzo-quinazolinyl, benzo-quinoxalinyl, acridinyl,phenazinyl, phenoxazinyl, phenothiazinyl, phenanthrolinyl, perimidinyl,phenanthridinyl, pteridinyl, naphthyridinyl, furanyl, pyranyl, oxazinyl,oxazolyl, oxadiazolyl, triazolyl, dioxanyl, benzo-furanyl,dibenzo-furanyl, thiopyranyl, xanthenyl, chromenyl, iso-chromenyl,thiazinyl, thiophenyl, benzo-thiophenyl, dibenzo-thiophenyl,difuro-pyrazinyl, benzofuro-dibenzo-furanyl,benzothieno-benzo-thiophenyl, benzothieno-dibenzo-thiophenyl,benzothieno-benzo-furanyl, benzothieno-dibenzo-furanyl, N-substitutedspiro-fluorenyl, spiro-fluoreno-acridinyl and spiro-fluoreno-xanthenyl.

In Formula 1, when the nuclear atoms X₁-X₈ constituting the centralfused hetero aromatic ring of the electron acceptor moiety include onenitrogen atom, the molecule does not have delayed fluorescent propertyand luminous property. On the contrary, when the nuclear atoms X₁-X₈constituting the central fused hetero aromatic ring of the electronacceptor moiety include three or more nitrogen atoms, the energy levelbandgap E_(g) between the HOMO energy level and the LUMO energy level ofthat molecule may be less than the energy level bandgap E_(g)between theHOMO energy level and the LUMO energy level of the second compound. Inthis case, exciton energy from the first compound DF to the secondcompound FD is not transferred sufficiently and the first compound DFemits mainly, ant therefore, it is not possible to implementhyper-fluorescence.

In another exemplary aspect, at least one, for example, at least two, ofR₁, which may constitute the electron donor moiety of the first compoundDF, may include a fused hetero aromatic group that includes three ormore aromatic or hetero aromatic rings, for example, three to sixaromatic or hetero aromatic rings with at least one nitrogen atom as anuclear atom. As an example, at least one, for example, at least two, ofR₁ may be a fused hetero aromatic group with at least one or twonitrogen atoms as a nuclear atom. For example, such a fused heteroaromatic group may be selected from, but is not limited to, the groupconsisting of a carbazolyl moiety, an acridinyl moiety, an acridonylmoiety, a phenazinyl moiety, a phenoxazinyl moiety and a phenothiazinylmoiety.

In an exemplary aspect, at least one, for example, at least two, of R₁may be selected from the group consisting of a carbazolyl group, anacridinyl group, an acridonyl group, a phenazinyl group, a phenoxazinylgroup and a phenothiazinyl group, each of which is not fused otherrings. Alternatively, at least one, for example, at least two, of R₁ maybe selected from the group consisting of a carbazolyl group, anacridinyl group, an acridonyl group, a phenazinyl group, a phenoxazinylgroup and a phenothiazinyl group, each of which is independently fusedother rings. In this case, the other ring fused to the such fused heteroaromatic group may comprise a benzene ring, a naphthalene ring, anindene ring, a pyridine ring, an indole ring, a furan ring, abenzo-furan ring, a dibenzo-furan ring, a thiophene ring, abenzo-thiophene ring, a dibenzo-thiophene ring and/or combinationthereof. For example, at least one, for example, at least two of R₁ maycomprise, but is not limited to, an indeno-carbazolyl group and/or anindolo-carbazolyl group. Alternatively, at least one, for example, atleast two, of R₁ may comprise, but is not limited to, aspiro-fluoreno-acridinyl group.

In another exemplary aspect, at least one, for example, at least two ofR₁ may comprise, but is not limited to, a carbazolyl moiety or anacridinyl moiety that is unsubstituted or substituted with at least oneselected from a C₁-C₁₀ alkyl group, a C₆-C₃₀ aryl group and a C₃-C₃₀hetero aryl group.

For example, the fused hetero aromatic group constituting R₁ may beunsubstituted or substituted with at least one selected from a C₁-C₁₀alkyl group (e.g. a C₁-C₅ alkyl group such as tert-butyl group), aC₆-C₃₀ aryl group (e.g. a C₆-C₁₅ aryl group such as phenyl) and a C₃-C₃₀hetero aryl group (e.g. a C₃-C₁₅ hetero aryl group such as pyridyl).

In another aspect, one of X₁ and X₄ may be CR₁ and the other of X₁ andX₄ may be N, X₂ and X₃ may be CR₁, one of X₅ and X₈ may be CR₁ and theother of X₅ and X₈ may be N and X₆ and X₇ may be CR₁. In other words,the fused hetero aromatic group as the electron acceptor moiety in thefirst compound DF may include, but is not limited to, a naphthyridinemoiety with two nitrogen atoms as a nuclear atom such as a1,8-naphthyridine moiety or a 1,5-naphthyridine moiety. The firstcompound DF having a naphthyridine ring as the electron acceptor moietymay have, but is not limited to, the following structure of Formula 2:

In Formula 2, one of Y₁ and Y₂ is CR₁₅ and the other of Y₁ and Y₂ is N;one of Y₃ and Y₄ is CR₁₆ and the other of Y₃ and Y₄ is N; each of R₁₁ toR₁₆ is independently selected from the group consisting of protium,deuterium, tritium, a halogen atom, an unsubstituted or substitutedsilyl group, an unsubstituted or substituted C₁-C₂₀ alkyl group, anunsubstituted or substituted C₁-C₂₀ alkyl amino group, an unsubstitutedor substituted C₆-C₃₀ aromatic group and an unsubstituted or substitutedC₃-C₃₀ hetero aromatic group, and wherein at least one of R₁₁ to R₁₆ isselected from the group consisting of an unsubstituted or substitutedcarbazolyl moiety, an unsubstituted or substituted acridinyl moiety, anunsubstituted or substituted acridonyl moiety, an unsubstituted orsubstituted phenazinyl moiety, an unsubstituted or substitutedphenoxazinyl moiety and an unsubstituted or substituted phenothiazinylmoiety.

As an example, each of the C₆-C₃₀ aromatic group and the C₃-C₃₀ heteroaromatic group of R₁₁ to R₁₆, for example, each of the carbazolylmoiety, the acridinyl moiety, the acridonyl moiety, the phenazinylmoiety, the phenoxazinyl moiety and the phenothiazinyl moiety may beindependently unsubstituted or substituted with at least one of a C₁-C₁₀alkyl group, a C₆-C₃₀ aryl group and a C₃-C₃₀ hetero aryl group.

The organic compound having the structure of Formula 2 has the delayedfluorescent property and has a singlet energy level, a triplet energylevel, a HOMO energy level and a LUMO energy level that can transfersufficient exciton energies to the second compound FD, as describedbelow. As an example, the first compound DF having the naphthyridinemoiety as the electron acceptor moiety may be selected from, but is notlimited to, the following compounds of the Formula 3:

The first compound DF of the delayed fluorescent material has verynarrow energy level bandgap ΔE_(ST) ^(DF) between a singlet energy levelS₁ ^(DF) and a triplet energy level T₁ ^(DF) (see, FIG. 7) and hasexcellent quantum efficiency because the triplet exciton energy of thefirst compound DF can be converted to the singlet exciton energy by RISCmechanism.

However, the first compound DF having the structure of Formulae 1 to 3has a distorted chemical conformation owing to the electron acceptormoiety and the electron donor moiety and requires addition chargetransfer transition (CT transition) because of utilizing tripletexcitons. The first compound DF having the structure of Formulae 1 to 3has very wide FWHM (full-width at half maximum) owing to theluminescence property caused by the CT luminous mechanism, thus itscolor purity is very limited.

The EML 240 includes the second compound FD of the fluorescent materialin order to maximize the luminous property of the first compound DF ofthe delayed fluorescent material and to implement hyper fluorescence. Asdescribed above, the first compound DF having the delayed fluorescentproperty can utilize the triplet exciton energy as well as the singletexciton energy. When the EML 240 includes the second compound FD of thefluorescent material having proper energy levels compared to the firstcompound DF of the delayed fluorescent material, the exciton energyemitted from the first compound DF is absorbed by the second compoundFD, and then the exciton energy absorbed by the second compound FDgenerates 100% singlet exciton with maximizing its luminous efficiency.

The singlet exciton energy of the first compound DF, which includes thesinglet exciton energy of the first compound DF converted from its owntriplet exciton energy and initial singlet exciton energy in the EML240, is transferred to the second compound FD of the fluorescentmaterial in the same EML 240 via Forster resonance energy transfer(FRET) mechanism, and the ultimate emission is occurred at the secondcompound FD. A compound having an absorption spectrum widely overlappedwith a photoluminescence spectrum of the first compound DF may be usedas the second compound FD so that the exciton energy generated at thefirst compound DF may be efficiently transferred to the second compoundFD. Since the second compound FD emits light with singlet excitonsshifted from the excited state to the ground state, not CT luminousmechanism, its FWHM is relatively narrow, and thus can improve colorpurity.

The second compound FD in the EML 240 may be blue fluorescent material.For example, the second compound FD in the EML 240 may be a boron-basedcompound with its FWHM equal to or less than about 35 nm. As an example,the second compound FD of the boron-based compound may have thefollowing structure of Formula 4:

In Formula 4, each of R₂₁ to R₂₄ is independently selected from thegroup consisting of protium, deuterium, tritium, boryl, amino, anunsubstituted or substituted C₁-C₂₀ alkyl group, an unsubstituted orsubstituted C₁-C₂₀ alkyl amino group, an unsubstituted or substitutedC₆-C₃₀ aromatic group and an unsubstituted or substituted C₃-C₃₀ heteroaromatic group, or adjacent two of R₂₁ to R₂₄ form an unsubstituted orsubstituted fused ring having boron and nitrogen, or an unsubstituted orsubstituted fused ring having sulfur; each of R₂₅ to R₂₈ isindependently selected from the group consisting of protium, deuterium,tritium, boryl, an unsubstituted or substituted C₁-C₂₀ alkyl group, anunsubstituted or substituted C₁-C₂₀ alkyl amino group, an unsubstitutedor substituted C₆-C₃₀ aromatic group and an unsubstituted or substitutedC₃-C₃₀ hetero aromatic group.

As an example, each of the C₆-C₃₀ aromatic group and the C₃-C₃₀ heteroaromatic group of R₂₁ to R₂₈ may be independently unsubstituted orsubstituted with at least one of a C₁-C₁₀ alkyl group, a C₆-C₃₀ arylgroup and a C₃-C₃₀ hetero aryl group. Similar to Formula 1, the C₆-C₃₀aromatic group, which can be constituted each of R₂₁ to Res, maycomprise independently, but is not limited to, a C₆-C₃₀ aryl group, aC₇-C₃₀ aryl alkyl group, a C₆-C₃₀ aryl oxy group and a C₆-C₃₀ aryl aminogroup. Alternatively, the C₃-C₃₀ hetero aromatic group, which can beconstitute each of R₂₁ to R₂₈, may comprise independently, but is notlimited to, a C₃-C₃₀ hetero aryl group, a C₄-C₃₀ hetero aryl alkylgroup, a C₃-C₃₀ hetero aryl oxy group and a C₃-C₃₀ hetero aryl aminogroup.

In one exemplary aspect, two adjacent groups of R₂₁ to R₂₄ in Formula 4may form a fused ring having boron and nitrogen atoms as a nuclear atom.For example, the second compound FD may include a boron-based organiccompound having the following structure of Formula 5A or Formula 5B:

In Formulae 5A and 5B, each of R₂₅ to R₂₈ and each of R₃₁ to R₃₄ isindependently selected from the group consisting of protium, deuterium,tritium, boryl, an unsubstituted or substituted C₁-C₂₀ alkyl group, anunsubstituted or substituted C₁-C₂₀ alkyl amino group, an unsubstitutedor substituted C₆-C₃₀ aromatic group and an unsubstituted or substitutedC₃-C₃₀ hetero aromatic group.

For example, each of the C₆-C₃₀ aromatic group and the C₃-C₃₀ heteroaromatic group, each of which can be independently each of R₂₅ to R₂₈and each of R₃₁ to R₃₄, may be independently unsubstituted orsubstituted with at least one of a C₁-C₁₀ alkyl group, a C₆-C₃₀ arylgroup and a C₃-C₃₀ hetero aryl group.

The boron-based compound having the structure of Formula 5A or 5B hasexcellent luminous properties. Also, since the boron-based compoundhaving the structure of Formula 5A or 5B has a wide plate-likeconformation, exciton energy from the first compound DF can beeffectively transferred to the second compound FD, and therefore, theOLED D1 can maximize its luminous efficiency.

In an exemplary aspect, the second compound FD of the boron-basedorganic compound may be selected from, but is not limited to, thefollowing compounds having the structure of Formula 6:

The third compound H in the EML 240 may be any organic compound havingwider energy level bandgap between a HOMO energy level and a LUMO energylevel compared to the first compound DF and/or the second compound FD.As an example, when the EML 240 includes the third compound H of thehost, the first compound DF may be a first dopant and the secondcompound FD may be a second dopant.

In an exemplary aspect, the third compound in the EML 240 may comprise,but is not limited to, 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP),3,3′-bis(N-carbazolyl)-1,1′-biphenyl (mCBP),1,3-Bis(carbazol-9-yl)benzene (mCP),9-(3-(9H-carbazol-9-yl)phenyl)-9H-carbazole-3-carbonitrile (mCP-CN),Bis[2-(diphenylphosphino)phenyl] ether oxide (DPEPO),2,8-bis(diphenylphosphoryl)dibenzothiophene (PPT),1,3,5-Tri[(3-pyridyl)-phen-3-yl]benzene (TmPyPB),2,6-Di(9H-carbazol-9-yl)pyridine (PYD-2Cz),2,8-di(9H-carbazol-9-yl)dibenzothiophene (DCzDBT),3,5-Di(carbazol-9-yl)-[1,1-bipheyl]-3,5-dicarbonitrile (DCzTPA),4-(9H-carbazol-9-yl)biphenyl-3,5-dicarbonitrile (pCzB-2CN),3′-(9H-carbazol-9-yl)biphenyl-3,5-dicarbonitrile (mCzB-2CN),Diphenyl-4-triphenyl silylphenyl-phosphine oxide (TSPO1),9-(9-phenyl-9H-carbazol-6-yl)-9H-carbazole (CCP),4-(3-(triphenylen-2-yl)phenyl)dibenzo[b,d]thiophene,9-(4-(9H-carbazol-9-yl)phenyl)-9H-3,9′-bicarbazole,9-(3-(9H-carbazol-9-yl)phenyl)-9H-3,9′-bicarbazole,9-(6-(9H-carbazol-9-yl)pyridin-3-yl)-9H-3,9′-bicabazole and combinationthereof.

In an exemplary aspect, when the EML 240 includes the first compound DF,the second compound FD and the third compound H, the contents of thethird compound H may be larger than the contents of the first compoundDF in the EML 240, and the contents of the first compound DF may belarger than the contents of the second compound FD in the EML 240. Whenthe contents of the first compound DF is larger than the contents of thesecond compound FD, exciton energy can be effectively transferred fromthe first compound DF to the second compound FD via FRET mechanism. Forexample, the contents of the third compound H in the EML 240 may beabout 65 wt % to about 90 wt %, the contents of the first compound DF inthe EML 240 may be about 5 wt % to about 30 wt %, and the contents ofthe second compound FD in the EML 240 may be about 0.1 wt % to about 5wt %, but is not limited thereto.

In one exemplary aspect, HOMO energy levels and LUMO energy levels amongthe third compound H of the host, the first compound DF of the delayedfluorescent material and the second compound FD of the fluorescentmaterial must be properly adjusted. For example, the host must inducethe triplet excitons generated at the delayed fluorescent material to beinvolved in the luminescence process without quenching as non-radiativerecombination in order to implement hyper fluorescence. To this end, theenergy levels among the third compound H of the host, the first compoundDF of the delayed fluorescent material and the second compound FD of thefluorescent material should be adjusted.

FIG. 4 is a schematic diagram illustrating energy levels among luminousmaterials in an EML are adjusted so that charges are transferredeffectively to the second compound. As illustrated in FIG. 4, the thirdcompound H as the host may be designed to have the HOMO energy levelHOMO^(H) deeper than the HOMO energy level HOMO^(DF) of the firstcompound DF of the delayed fluorescent material, and to have the LUMOenergy level LUMO^(H) shallower than the LUMO energy level LUMO^(DF) ofthe first compound DF. In other words, the energy level bandgap betweenthe HOMO energy level HOMO^(H) and the LUMO energy level LUMO^(H) of thethird compound H may be wider than the energy level bandgap between theHOMO energy level HOMO^(DF) and the LUMO energy level LUMO^(DF) of thefirst compound DF.

As an example, an energy level bandgap (|HOMO^(H)-HOMO^(DF)|) betweenthe HOMO energy level (HOMO^(H)) of the third compound H of the host andthe HOMO energy level (HOMO^(DF)) of the first compound DF of thedelayed fluorescent material, or an energy level bandgap(|LUMO^(H)-LUMO^(DF)|) between the LUMO energy level (LUMO^(H)) of thethird compound H and the LUMO energy level (LUMO^(DF)) of the firstcompound DF may be equal to or less than about 0.5 eV, for example,between about 0.1 eV to about 0.5 eV. In this case, the charges can betransported efficiently from the third compound H to the first compoundDF and thereby enhancing the ultimate luminous efficiency in the OLEDD1.

In one exemplary aspect, the energy level bandgap ΔHOMO-1 between theHOMO energy level HOMO^(DF) of the first compound DF and the HOMO energylevel HOMO^(FD) of the second compound FD satisfies the followingrelationship in Equation (1):

|HOMO^(FD)−HOMO^(DF)|<0.3 eV  (1).

When the energy level bandgap ΔHOMO-1 between the HOMO energy levelHOMO^(DF) of the first compound DF and the HOMO energy level HOMO^(FD)of the second compound FD satisfies the relationship in Equation (1),holes injected into the EML 240 may be transferred to the first compoundDF. Accordingly, the first compound DF can utilize both the initialsinglet exciton energy and the singlet exciton energy converted from thetriplet exciton energy by RISC mechanism so that it can implement 100%of internal quantum efficiency and can transfer efficiently its excitonenergy to the second compound FD. As an example, the HOMO energy levelHOMO^(DF) of the first compound DF and the HOMO energy level HOMO^(FD)of the second compound FD may satisfy the following relationship inEquation (2):

|HOMO^(FD)−HOMO^(DF)|≤0.2 eV  (2).

In another exemplary aspect, the LUMO energy level LUMO^(DF) of thefirst compound DF may be shallower than or equal to the LUMO energylevel LUMO^(FD) of the second compound FD. As an example, the LUMOenergy level LUMO^(DF) of the first compound DF and the LUMO energylevel LUMO^(FD) of the second compound FD may satisfy the followingrelationship in Equation (3):

0≤LUMO^(DF)−LUMO^(FD)≤0.5 eV  (3).

When the LUMO energy level LUMO^(DF) of the first compound DF and theLUMO energy level LUMO^(FD) of the second compound FD satisfy therelationship in Equation (3), electrons injected into the EML 240 can betransferred to the first compound DF. As excitons can be recombined inthe first compound DF of the delayed fluorescent material, the firstcompound DF can implement 100% of internal quantum efficiency using RISCmechanism. The singlet exciton energy including the initial singletexciton energy and the converted singlet exciton energy generated at thefirst compound DF can be transferred to the second compound FD of thefluorescent material via FRET, and therefore, the second compound FD canrealize efficient emission.

As an example, the first compound DF may be designed, but is not limitedto, to have the HOMO energy level HOMO^(DF) between about −5.4 eV and−5.7 eV and to have the LUMO energy level LUMO^(DF) between about −2.4eV and −2.8 eV. The second compound FD may be designed, but is notlimited to, to have the HOMO energy level HOMO^(FD) between about −5.3eV and about −5.7 eV and to have the LUMO energy level LUMO^(FD) betweenabout −2.7 eV and about −3.0 eV.

The energy level bandgap between the HOMO energy level HOMO^(DF) and theLUMO energy level LUMO^(DF) of the first compound DF may be wider thanthe energy level bandgap between the HOMO energy level HOMO^(FD) and theLUMO energy level LUMO^(FD) of the second compound FD. For example, thefirst compound DF may have the energy level bandgap between the HOMOenergy level HOMO^(DF) and the LUMO energy level LUMO^(DF) between about2.6 eV and about 3.1 eV, for example, about 2.8 eV and about 3.0 eV. Thesecond compound FD may have the energy level bandgap between the HOMOenergy level HOMO^(FD) and the LUMO energy level LUMO^(FD) between about2.4 eV and about 2.9 eV, for example, about 2.6 eV and about 2.8 eV. Inthis case, the exciton energy generated at the first compound DF can betransferred efficiently to the second compound FD, and then the secondcompound FD can emit light sufficiently.

FIG. 5 is a schematic diagram illustrating HOMO energy levels amongluminous material in an EML are not adjusted so that holes are trappedat the second compound. As illustrated in FIG. 5, when an energy levelbandgap ΔHOMO-2 between the HOMO energy level HOMO^(DF) of the firstcompound DF and the HOMO energy level HOMO^(FD) of the second compoundFD is equal to or more than 0.3 eV, holes injected into the EML 240 aretrapped at the second compound FD of the fluorescent material. Namely,holes injected into the EML 240 are not transferred to the firstcompound DF of the delayed fluorescent material from the third compoundH of the host. Excitons are not formed in the first compound DF that canutilize both the singlet and triplet energies, but holes trapped at thesecond compound FD of the fluorescent material that can utilize only thesinglet excitons are recombined to form excitons and to emit light.Triplet exciton energy cannot be involved in the luminous process, butis quenched as non-radiative recombination, thus causes the EML todecrease its luminous efficiency.

FIG. 6 is a schematic diagram illustrating both HOMO and LUMO energylevels among luminous material in an EML are not adjusted so that holesare trapped at the second compound and an exciplex are formed betweenthe first and second compounds. As illustrated in FIG. 6, when an energylevel bandgap ΔHOMO-3 between the HOMO energy level HOMO^(DF) of thefirst compound DF and the HOMO energy level HOMO^(FD) of the secondcompound FD is equal to or more than 0.5 eV, holes injected into the EML240 are trapped at the second compound FD of the fluorescent material.

In addition, when the LUMO energy level LUMO^(DF) of the first compoundDF is deeper than the LUMO energy level LUMO^(FD) of the second compoundFD (i.e., LUMO^(FD)>LUMO^(DF)), holes trapped at the second compound FDand electrons transferred to the first compound DF form an exciplex.Triplet exciton energy is quenched as a non-radiative recombination,which causes the EML to decrease its luminous efficiency. In addition,as the energy level bandgap between the LUMO energy level and HOMOenergy level forming the exciplex is too narrow, the EML emits lighthaving long wavelength. As both the first compound DF and the secondcompound FD emit simultaneously, the light emitted from the EML has wideFWHM and bad color purity.

Now, we will describe the luminous mechanism in the EML 240. FIG. 7 is aschematic diagram illustrating a luminous mechanism by singlet andtriplet energy levels among luminous materials in an EML in accordancewith one exemplary aspect of the present disclosure. As illustrated inFIG. 7, the singlet energy level S₁ ^(H) of the third compound H, whichcan be the host in the EML 240, is higher than the singlet energy levelS₁ ^(DF) of the first compound DF having the delayed fluorescentproperty. In addition, the triplet energy level T₁ ^(DF) of the thirdcompound H may be higher than the triplet energy level T₁ ^(DF) of thefirst compound DF. As an example, the triplet energy level T₁ ^(H) ofthe third compound H may be higher than the triplet energy level T₁^(DF) of the first compound DF by at least about 0.2 eV, for example, atleast about 0.3 eV such as at least about 0.5 eV.

When the triplet energy level T₁ ^(H) and/or the singlet energy level S₁^(H) of the third compound H is not high enough than the triplet energylevel T₁ ^(DF) and/or the singlet energy level S₁ ^(DF) of the firstcompound DF, the triplet state exciton energy of the first compound DFmay be reversely transferred to the triplet energy level T₁ ^(H) of thethird compound H. In this case, the triplet exciton reverselytransferred to the third compound H where the triplet exciton cannot beemitted is quenched as non-emission so that the triplet exciton energyof the first compound DF having the delayed fluorescent property cannotcontribute to luminescence. As an example, the first compound DF havingthe delayed fluorescent property may have the energy level bandgapΔE_(ST) ^(DF) between the singlet energy level S₁ ^(DF) and the tripletenergy level T₁ ^(DF) equal to or less than about 0.3 eV, for examplebetween about 0.05 eV and about 0.3 eV.

In addition, the singlet exciton energy, which is generated at the firstcompound DF of the delayed fluorescent material that is converted to ICTcomplex by RISC in the EML 240, should be efficiently transferred to thesecond compound FD of the fluorescent material so as to implement OLEDD1 having high luminous efficiency and high color purity. To this end,the singlet energy level S₁ ^(DF) of the first compound DF of thedelayed fluorescent material is higher than the singlet energy level S₁^(FD) of the second compound FD of the fluorescent material. Optionally,the triplet energy level T₁ ^(DF) of the first compound DF may be higherthan the triplet energy level T₁ ^(DF) of the second compound FD.

Returning to FIG. 3, the HIL 250 is disposed between the first electrode210 and the HTL 260 and improves an interface property between theinorganic first electrode 210 and the organic HTL 260. In one exemplaryaspect, the HIL 250 may include, but is not limited to,4,4′,4″-Tris(3-methylphenylamino)triphenylamine (MTDATA),4,4′,4″-Tris(N,N-diphenyl-amino)triphenylamine (NATA),4,4′,4″-Tris(N-(naphthalene-1-yl)-N-phenyl-amino)triphenylamine(1T-NATA),4,4′,4″-Tris(N-(naphthalene-2-yl)-N-phenyl-amino)triphenylamine(2T-NATA), Copper phthalocyanine (CuPc),Tris(4-carbazoyl-9-yl-phenyl)amine (TCTA),N,N′-Diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4″-diamine (NPB;NPD), 1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile(Dipyrazino[2,3-f:2′3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile;HAT-CN), 1,3,5-tris[4-(diphenylamino)phenyl]benzene (TDAPB),poly(3,4-ethylenedioxythiphene)polystyrene sulfonate (PEDOT/PSS),N-(biphenyl-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amineand combination thereof. The HIL 250 may be omitted in compliance with astructure of the OLED D1.

The HTL 260 is disposed between the HIL 250 and the EML 240. In oneexemplary aspect, the HTL 260 may include, but is not limited to,N,N′-Diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD),NPB, CBP, Poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)-benzidine](Poly-TPD),Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)diphenylamine))](TFB), Di[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane (TAPC),5-Di(9H-carbazol-9-yl)-N,N-diphenylaniline (DCDPA),N-(biphenyl-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluoren-2-amine,N-(biphenyl-4-yl)-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)biphenyl-4-amineand combination thereof.

The ETL 270 and the EIL 280 may be laminated sequentially between theEML 240 and the second electrode 230. The ETL 270 includes materialhaving high electron mobility so as to provide electrons stably with theEML 240 by fast electron transportation. In one exemplary aspect, theETL 270 may comprise, but is not limited to, any one of oxadiazole-basedcompounds, triazole-based compounds, phenanthroline-based compounds,benzoxazole-based compounds, benzothiazole-based compounds,benzimidazole-based compounds, triazine-based compounds, and the like.

As an example, the ETL 270 may comprise, but is not limited to,tris-(8-hydroxyquinoline aluminum (Alq3),2-biphenyl-4-yl-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD), spiro-PBD,lithium quinolate (Liq), 1,3,5-Tris(N-phenylbenzimidazol-2-yl)benzene(TPBi),Bis(2-methyl-8-quinolinolato-N1,O8)-(1,1′-biphenyl-4-olato)aluminum(BAlq), 4,7-diphenyl-1,10-phenanthroline (Bphen),2,9-Bis(naphthalene-2-yl)4,7-diphenyl-1,10-phenanthroline (NBphen),2,9-Dimethyl-4,7-diphenyl-1,10-phenaathroline (BCP),3-(4-Biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ),4-(Naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole (NTAZ),1,3,5-Tri(p-pyrid-3-yl-phenyl)benzene (TpPyPB),2,4,6-Tris(3′-(pyridin-3-yl)biphenyl-3-yl)1,3,5-triazine (TmPPPyTz),Poly[9,9-bis(3′-(N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene]-alt-2,7-(9,9-dioctylfluorene)](PFNBr), tris(phenylquinoxaline) (TPQ), TSPO1 and combination thereof.

The EIL 280 is disposed between the second electrode 230 and the ETL270, and can improve physical properties of the second electrode 230 andtherefore, can enhance the luminous lifespan of the OLED D1. In oneexemplary aspect, the EIL 280 may comprise, but is not limited to, analkali metal halide or an alkaline earth metal halide such as LiF, CsF,NaF, BaF₂ and the like, and/or an organic metal compound such as lithiumquinolate, lithium benzoate, sodium stearate, and the like.

When holes are transferred to the second electrode 230 via the EML 240and/or electrons are transferred to the first electrode 210 via the EML240, the OLED D1 may have short lifespan and reduced luminousefficiency. In order to prevent these phenomena, the OLED D1 inaccordance with this aspect of the present disclosure may have at leastone exciton blocking layer adjacent to the EML 240.

For example, the OLED D1 of the exemplary aspect includes the EBL 265between the HTL 260 and the EML 240 so as to control and preventelectron transfers. In one exemplary aspect, the EBL 265 may comprise,but is not limited to, TCTA, Tris[4-(diethylamino)phenyl]amine,N-(biphenyl-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)-9H-fluorene-2-amine,TAPC, MTDATA, mCP, mCBP, CuPc,N,N′-bis[4-(bis(3-methylphenyl)amino)phenyl]-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(DNTPD), TDAPB, 3,6-bis(N-carbazolyl)-N-phenyl-carbazole and combinationthereof.

In addition, the OLED D1 may further include the HBL 275 as a secondexciton blocking layer between the EML 240 and the ETL 270 so that holescannot be transferred from the EML 240 to the ETL 270. In one exemplaryaspect, the HBL 275 may comprise, but is not limited to, any one ofoxadiazole-based compounds, triazole-based compounds,phenanthroline-based compounds, benzoxazole-based compounds,benzothiazole-based compounds, benzimidazole-based compounds, andtriazine-based compounds each of which can be used in the ETL 270.

For example, the HBL 275 may comprise a compound having a relatively lowHOMO energy level compared to the HOMO energy level of the luminescentmaterials in EML 240. The HBL 275 may comprise, but is not limited to,BCP, BAlq, Alq3, PBD, spiro-PBD, Liq,Bis-4,5-(3,5-di-3-pyridylphenyl)-2-methylpyrimidine (B3PYMPM), DPEPO,9-(6-(9H-carbazol-9-yl)pyridine-3-yl)-9H-3,9′-bicarbazole andcombination thereof.

In the above aspect, the first compound having the delayed fluorescentmaterial and the second compound having the fluorescent material areincluded within the same EML. Unlike that aspect, the first compound andthe second compound are included in separate EMLs. FIG. 8 is a schematiccross-sectional view illustrating an OLED in accordance with anotherexemplary aspect of the present disclosure. FIG. 9 is a schematicdiagram illustrating energy levels among luminous materials in EMLs areadjusted so that holes are transferred to the second compound. FIG. 10is a schematic diagram illustrating a luminous mechanism by singlet andtriplet energy levels among luminous materials in EMLs in accordancewith another exemplary aspect of the present disclosure.

As illustrated in FIG. 8, the OLED D2 includes first and secondelectrodes 310 and 330 facing each other and an emissive layer 320having single emitting part disposed between the first and secondelectrodes 310 and 330. The organic light emitting display device 100(FIG. 2) includes a red pixel region, a green pixel region and a bluepixel region, and the OLED D2 may be disposed in the blue pixel region.

In one exemplary aspect, the emissive layer 320 comprises adouble-layered EML 340. Also, the emissive layer 320 may comprise atleast one of an HTL 360 disposed between the first electrode 310 and theEML 340 and an ETL 370 disposed between the second electrode 230 and theEML 340. Also, the emissive layer 320 may further comprise at least oneof an HIL 350 disposed between the first electrode 310 and the HTL 360and an EIL 380 disposed between the second electrode 330 and the ETL370. Alternatively, the emissive layer 320 may further comprise an EBL365 disposed between the HTL 360 and the EML 340 and/or a HBL 375disposed between the EML 340 and the ETL 370. The configuration of thefirst and second electrodes 310 and 330 as well as other layers exceptthe EML 340 in the emissive layer 320 may be substantially identical tothe corresponding electrodes and layers in the OLED D1.

The EML 340 comprises a first EML (EML1, lower EML, first layer) 342disposed between the EBL 365 and the HBL 375 and a second EML (EML2,upper EML, second layer) 344 disposed between the EML1 342 and the HBL375. Alternatively, the EML 344 may be disposed between the EBL 365 andthe EML1 342.

One of the EML1 342 and the EML2 344 includes the first compound (firstdopant) DF of the delayed fluorescent material, and the other of theEML1 342 and the EML2 344 includes the second compound (second dopant)FD of the fluorescent material. Also, each of the EML1 342 and the EML2344 includes a fourth compound (Compound 4) H1 of a first host and afifth compound (Compound 5) H2 of a second host. As an example, the EML1342 may include the first compound DF and the fourth compound H1 and theEML2 344 may include the second compound FD and the fifth compound H2.

The first compound DF in the EML1 342 may comprise any delayedfluorescent material having the structure of Formulae 1 to 3. Thetriplet exciton energy of the first compound DF having delayedfluorescent property can be converted upwardly to its own singletexciton energy via RISC mechanism. While the first compound DF has highinternal quantum efficiency, but it has poor color purity due to itswide FWHM.

The EML2 344 comprises the second compound FD of the florescentmaterial. The second compound FD includes any organic compound havingthe structure of Formulae 4 to 6. While the second compound FD of thefluorescent material having the structure of Formulae 4 and 6 has anadvantage in terms of color purity due to its narrow FWHM, but itsinternal quantum efficiency is low because its triplet exciton cannot beinvolved in the luminescence process.

However, in this exemplary aspect, the singlet exciton energy as well asthe triplet exciton energy of the first compound DF having the delayedfluorescent property in the EML1 342 can be transferred to the secondcompound FD in the EML2 344 disposed adjacently to the EML1 342 by FRETmechanism, and the ultimate light emission occurs in the second compoundFD within the EML2 344.

In other words, the triplet exciton energy of the first compound DF isconverted upwardly to its own singlet exciton energy in the EML1 342 byRISC mechanism. Then, both the initial singlet exciton energy and theconverted singlet exciton energy of the first compound DF is transferredto the singlet exciton energy of the second compound FD in the EML2 344.The second compound FD in the EML2 344 can emit light using the tripletexciton energy as well as the singlet exciton energy. As the singletexciton energy generated at the first compound DF in the EML1 342 isefficiently transferred to the second compound FD in the EML2 344, theOLED D2 can implement hyper fluorescence. In this case, while the firstcompound DF having the delayed fluorescent property only acts astransferring exciton energy to the second compound FD, substantial lightemission is occurred in the EML2 344 including the second compound FD.The OLED D2 can enhance quantum efficiency and color purity owing tonarrow FWHM.

As described above, the first compound DF of the delayed fluorescentmaterial includes the organic compound having the structure of Formulae1 to 3 and the second compound FD of the fluorescent material includesthe boron-based organic compound having the structure of Formulae 4 to6. The fourth compound H1 may be identical to or different from thefifth compound H2. For example, each of the fourth compound H1 and thefifth compound H2 may include, but is not limited to, the third compoundH described above, respectively.

Similar to the first aspect, the energy level bandgap ΔHOMO-1 betweenthe HOMO energy level HOMO^(DF) of the first compound DF and the HOMOenergy level HOMO^(FD) of the second compound FD may satisfy therelationship in Equation (1) or (2) as described above. In this case,holes injected into the EML 340 are transferred efficiency to the firstcompound DF so that the first compound DF can utilize both the singletand triplet exciton energies and transfer the exciton energies to thesecond compound FD. In addition, the LUMO energy level LUMO^(DF) of thefirst compound DF may be shallower than or equal to the LUMO energylevel LUMO^(FD) of the second compound FD, and may satisfy therelationship in Equation (3) as described above.

Also, an energy level bandgap (|HOMO^(H)-HOMO^(DF)|) between the HOMOenergy levels (HOMO^(H1) and HOMO^(H2)) of the fourth and fifthcompounds H1 and H2 and the HOMO energy level (HOMO^(DF)) of the firstcompound DF, or an energy level bandgap (|LUMO^(H)-LUMO^(DF)|) betweenthe LUMO energy levels (LUMO^(H1) and LUMO^(H2)) of the fourth and fifthcompounds H1 and H2 and the LUMO energy level (LUMO^(DF)) of the firstcompound DF may be equal to or less than about 0.5 eV. The HOMO or LUMOenergy level bandgap between the fourth and fifth compounds and thefirst compound does not satisfy hat condition, the exciton energy at thefirst compound DF may be quenched as a non-radiative recombination, orexciton energies may not be transferred efficiently to the firstcompound DF and/or the second compound FD from the fourth and fifthcompounds H1 and H2, thus the internal quantum efficiency in the OLED D2may be reduced.

Also, each of the exciton energies generated in each of the fourthcompound H1 in the EML1 342 and the fifth compound H2 in the EML2 344should be transferred primarily to the first compound DF of the delayedflorescent material and then to the second compound FD of thefluorescent materialin order to realize efficient light emission. Asillustrated in FIG. 10, each of the singlet energy levels S₁ ^(H)1 andS₁ ^(H2) of the fourth and fifth compounds H1 and H2 is higher than thesinglet energy level S₁ ^(DF) of the first compound DF having thedelayed fluorescent property. Also, each of the triplet energy levels T₁^(H1) and T₁ ^(H2) of the fourth and fifth compounds H1 and H2 may behigher than the triplet energy level T₁ ^(DF) of the first compound DF.For example, the triplet energy levels T₁ ^(H1) and T₁ ^(H2) of thefourth and fifth compound H1 and H2 may be higher than the tripletenergy level T₁ ^(DF) of the first compound DF by at least about 0.2 eV,for example, by at least 0.3 eV such as by at least 0.5 eV.

Also, the singlet energy level S₁ ^(H2) of the fifth compound H2 of thesecond host is higher than the singlet energy level S₁ ^(FD) of thesecond compound FD of the fluorescent material. Optionally, the tripletenergy level T₁ ^(H2) of the fifth compound H2 may be higher than thetriplet energy level T₁ ^(FD) of the second compound FD. In this case,the singlet exciton energy generated at the fifth compound H2 may betransferred to the singlet energy of the second compound FD.

In addition, the singlet exciton energy, which is generated at the firstcompound DF having the delayed fluorescent property that is converted toICT complex by RISC in the EML1 342, should be efficiently transferredto the second compound FD of the fluorescent material in the EML2 344.To this end, the triplet energy level S₁ ^(DF) of the first compound DFof the delayed fluorescent material in the EML1 342 is higher than thesinglet energy level S₁ ^(FD) of the second compound FD of thefluorescent material in the EML2 344. Optionally, the triplet energylevel T₁ ^(DF) of the first compound DF in the EML1 342 may be higherthan the triplet energy level T₁ ^(FD) of the second compound FD in theEML2 344

Each of the contents of the fourth and fifth compounds H1 and H2 in theEML1 342 and the EML2 344 may be larger than or identical to each of thecontents of the first and second compounds DF and FD in the same layer,respectively. Also, the contents of the first compound DF in the EML1342 may be larger than the contents of the second compound FD in theEML2 344. In this case, exciton energy is efficiently transferred fromthe first compound DF to the second compound FD via FRET mechanism. Asan example, the EML1 342 may comprise the first compound DF betweenabout 1 wt % and about 50 wt %, for example, about 10 wt % and about 40wt % such as about 20 wt % and about 40 wt %. The EML2 344 may comprisethe second compound FD between about 1 wt % and about 10 wt %, forexample, about 1 wt % and 5 wt %.

In one exemplary aspect, when the EML2 344 is disposed adjacently to theHBL 375, the fifth compound H2 in the EML4 344 may be the same materialas the HBL 375. In this case, the EML2 344 may have a hole blockingfunction as well as an emission function. In other words, the EML2 344can act as a buffer layer for blocking holes. In one aspect, the HBL 375may be omitted where the EML2 344 may be a hole blocking layer as wellas an emitting material layer.

In another aspect, when the EML2 344 is disposed adjacently to the EBL365, the fifth compound H2 in the EML2 344 may be the same as the EBL365. In this case, the EML2 344 may have an electron blocking functionas well as an emission function. In other words, the EML2 344 can act asa buffer layer for blocking electrons. In one aspect, the EBL 365 may beomitted where the EML2 344 may be an electron blocking layer as well asan emitting material layer.

An OLED having a triple-layered EML will be explained. FIG. 11 is aschematic cross-sectional view illustrating an OLED having atriple-layered EML in accordance with another exemplary aspect of thepresent disclosure. FIG. 12 is a schematic diagram illustrating energylevels among luminous materials in EMLs are adjusted so that holes aretransferred to the second compound. FIG. 13 is a schematic diagramillustrating luminous mechanism by energy level bandgap among luminousmaterials in accordance with another exemplary aspect of the presentdisclosure.

As illustrated in FIG. 11, the OLED D3 comprises first and secondelectrodes 410 and 430 facing each other and an emissive layer 420disposed between the first and second electrodes 410 and 430. Theorganic light emitting display device 100 (FIG. 2) includes a red pixelregion, a green pixel region and a blue pixel region, and the OLED D3may be disposed in the blue pixel region.

In one exemplary aspect, the emissive layer 420 having single emittingpart comprises a triple-layered EML 440. The emissive layer 420 maycomprise at least one of an HTL 460 disposed between the first electrode410 and the EML 440 and an ETL 370 disposed between the second electrode430 and the EML 440. Also, the emissive layer 420 may further compriseat least one of an HIL 450 disposed between the first electrode 410 andthe HTL 460 and an EIL 480 disposed between the second electrode 420 andthe ETL 470. Alternatively, the emissive layer 420 may further comprisean EBL 465 disposed between the HTL 460 and the EML 440 and/or a HBL 475disposed between the EML 440 and the ETL 470. The configurations of thefirst and second electrodes 410 and 430 as well as other layers exceptthe EML 440 in the emissive layer 420 is substantially identical to thecorresponding electrodes and layers in the OLEDs D1 and D2.

The EML 440 comprises a first EML (EML1, middle EML, first layer) 442, asecond EML (EML2, lower EML, second layer) 444 and a third EML (EML3,upper EML, third layer) 446. The EML1 442 is disposed between the EBL465 and the HBL 475, the EML2 444 is disposed between the EBL 465 andthe EML1 442 and the EML3 446 is disposed between the EML1 442 and theHBL 475.

The EML1 442 includes the first compound (first dopant) DF of thedelayed fluorescent material. Each of the EML2 444 and the EML3 446includes the second compound (second dopant) FD1 and a sixth compound(Compound 6, third dopant) FD2 each of which is the fluorescentmaterial, respectively. Also, each of the EML1 442, the EML2 444 and theEML3 446 includes the fourth compound H1 of the first host, the fifthcompound H2 of the second host and a seventh compound (Compound 7) H3 ofa third host, respectively.

In accordance with this aspect, both the singlet energy as well as thetriplet energy of the first compound DF of the delayed fluorescentmaterial in the EML 442 can be transferred to the second and sixthcompounds FD1 and FD2 of the fluorescent materials each of which isincluded in the EML2 444 and EML3 446 disposed adjacently to the EML1442 by FRET energy transfer mechanism. Accordingly, the ultimateemission occurs in the second and sixth compounds FD1 and FD2 in theEML2 444 and the EML3 446.

In other words, the triplet exciton energy of the first compound DFhaving the delayed fluorescent property in the EML1 442 is convertedupwardly to its own singlet exciton energy by RISC mechanism, then thesinglet exciton energy including the initial and converted singletexciton energy of the first compound DF is transferred to the singletexciton energy of the second and sixth compounds FD1 and FD2 in the EML2444 and the EML3 446 because the first compound DF has the singletenergy level S₁ ^(DF) higher than each of the singlet energy levels S₁^(FD1) and S₁ ^(FD2) of the second and sixth compounds FD1 and FD2 (FIG.13). The singlet exciton energy of the first compound DF in the EML1 442is transferred to the second and sixth compounds FD1 and FD2 in the EML2444 and the EML3 446 which are disposed adjacently to the EML1 442 byFRET mechanism.

The second and sixth compounds FD1 and FD2 in the EML2 444 and EML3 446can emit light using both the singlet exciton energy and the tripletexciton energy derived from the first compound DF. Each of the secondand sixth compounds FD1 and FD2 has relatively narrow FWHM compared tothe first compound DF. In this aspect, the OLED D3 can improve itsquantum efficiency and color purity owing to narrow FWHM, and theultimate emission occurs in the second and sixth compounds FD1 and FD2within the EML2 444 and the EML3 446.

The first compound DF of the delayed fluorescent material comprises anyorganic compound having the structure of Formulae 1 to 3. Each of thesecond and sixth compounds FD1 and FD2 of the fluorescent materialcomprises independently any boron-based organic compound having thestructure of Formulae 4 to 6. For example, the sixth compound FD2 maycomprise the second compound FD1. The fourth compound H1, the fifthcompound H2 and the seventh compound H3 may be identical to or differentfrom each other. For example, each of the fourth compound H1, the fifthcompound H2 and the seventh compound H3 may include, but is not limitedto, the third compound H described above, respectively.

Similar to the first and second aspects, the energy level bandgapΔHOMO-1 between the HOMO energy level HOMO^(DF) of the first compound DFand each of the HOMO energy level HOMO^(DF2) and HOMO^(DF3) of thesecond compound DF2 and the sixth compound DF3 may satisfy therelationship in Equation (1) or (2) as described above. In this case,holes injected into the EML 340 are transferred efficiency to the firstcompound DF so that the first compound DF can utilize both the singletand triplet exciton energies and transfer the exciton energies to boththe second compound FD1 and the sixth compound FD2. In addition, theLUMO energy level LUMO^(DF) of the first compound DF may be shallowerthan or equal to the LUMO energy levels LUMO^(FD1) and LUMO^(FD2) of thesecond compound FD1 and the sixth compound FD2, and may satisfy therelationship in Equation (3) as described above.

Also, an energy level bandgap (|HOMO^(H)-HOMO^(DF)|) between the HOMOenergy levels (HOMO^(H1), HOMO^(H2) and HOMO^(H3)) of the fourth, fifthand seventh compounds H1, H2 and H3 and the HOMO energy level(HOMO^(DF)) of the first compound DF, or an energy level bandgap(|LUMO^(H)-LUMO^(DF)|) between the LUMO energy levels (LUMO^(H1),LUMO^(H2) and LUMO^(H3)) of the fourth, fifth and seventh compounds H1,H2 and H3 and the LUMO energy level (LUMO^(DF)) of the first compound DFmay be equal to or less than about 0.5 eV.

Also, the singlet and triplet energy levels among the luminous materialsshould be properly adjusted in order to implement efficientluminescence. Referring to FIG. 13, each of the singlet energy levels S₁^(H1), S₁ ^(H2) and S₁ ^(H3) of the fourth, fifth and seventh compoundsH1, H2 and H3 of the first to third hosts is higher than the singletenergy level S₁ ^(DF) of the first compound DF having the delayedfluorescent property. Also, each of the triplet energy levels T₁ ^(H1),T₁ ^(H2) and T₁ ^(H3) of the fourth, fifth and seventh compounds H1, H2and H3 may be higher than the triplet energy level T₁ ^(DF) of the firstcompound DF.

In addition, the singlet exciton energy, which is generated at the firstcompound DF having the delayed fluorescent property that is converted toICT complex by RISC in the EML1 442, should be efficiently transferredto each of second and sixth compounds FD1 and FD2 of the fluorescentmaterial in the EML2 444 and the EML3 446. To this end, the tripletenergy level S₁ ^(DF) of the first compound DF of the delayedfluorescent material in the EML1 442 is higher than each of the singletenergy levels S₁ ^(FD1) and S₁ ^(FD2) of the second and sixth compoundsFD1 and FD2 of the fluorescent material in the EML2 444 and the EML3446. Optionally, the triplet energy level T₁ ^(DF) of the first compoundDF in the EML1 442 may be higher than each of the triplet energy levelsT₁ ^(FD1) and T₁ ^(FD2) of the second and sixth compounds FD1 and FD2 inthe EML2 444 and the EML3 446.

In addition, exciton energy transferred to each of the second and sixthcompounds FD1 and FD2 from the first compound DF should not transferredto each of the fifth and seventh compounds H2 and H3 in order to realizeefficient luminescence. To this end, each of the singlet energy levelsS₁ ^(H2) and S₁ ^(H3) of the fifth and seventh compounds H2 and H3, eachof which may be the second host and the third host, is higher than eachof the singlet energy levels S₁ ^(FD1) and S₁ ^(FD2) of the second andsixth compounds FD1 and FD2 of the fluorescent material, respectively.Optionally, each of the triplet energy level T₁ ^(H2) and T₁ ^(H3) ofthe fifth and seventh compounds H2 and H3 is higher than each of thetriplet energy levels T₁ ^(FD1) and T₁ ^(FD2) of the second and sixthcompounds FD1 and FD2, respectively.

The contents of the first compound DF in the EML1 442 may be larger thaneach of the contents of the second and sixth compounds FD1 and FD2 inthe EML2 444 or the EML3 446. In this case, exciton energy can betransferred sufficiently from the first compound DF in the EML1 442 toeach of the second and sixth compounds FD1 and FD2 in the EML2 444 andthe EML3 446 via FRET mechanism. As an example, the EML1 442 maycomprise the first compound DF between about 1 wt % and about 50 wt %,for example, about 10 wt % and about 40 wt % such as about 20 wt % andabout 40 wt %. Each of the EML2 444 and the EML3 446 may comprise thesecond or sixth compound FD1 and FD2 between about 1 wt % and about 10wt %, for example, about 1 wt % and 5 wt %.

In one exemplary aspect, when the EML2 444 is disposed adjacently to theEBL 465, the fifth compound H2 in the EML 444 may be the same materialas the EBL 465. In this case, the EML2 444 may have an electron blockingfunction as well as an emission function. In other words, the EML2 444can act as a buffer layer for blocking electrons. In one aspect, the EBL465 may be omitted where the EML2 444 may be an electron blocking layeras well as an emitting material layer.

When the EML3 446 is disposed adjacently to the HBL 475, the seventhcompound H3 in the EML3 446 may be the same material as the HBL 475. Inthis case, the EML3 446 may have a hole blocking function as well as anemission function. In other words, the EML3 446 can act as a bufferlayer for blocking holes. In one aspect, the HBL 475 may be omittedwhere the EML3 446 may be a hole blocking layer as well as an emittingmaterial layer.

In still another exemplary aspect, the fifth compound H2 in the EML2 444may be the same material as the EBL 455 and the seventh compound H3 inthe EML3 446 may be the same material as the HBL 475. In this aspect,the EML2 444 may have an electron blocking function as well as anemission function, and the EML3 446 may have a hole blocking function aswell as an emission function. In other words, each of the EML2 444 andthe EML3 446 can act as a buffer layer for blocking electrons or hole,respectively. In one aspect, the EBL 465 and the HBL 475 may be omittedwhere the EML2 444 may be an electron blocking layer as well as anemitting material layer and the EML3 446 may be a hole blocking layer aswell as an emitting material layer.

In an alternative aspect, an OLED may include multiple emitting parts.FIG. 14 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure.

As illustrated in FIG. 14, the OLED D4 comprises first and secondelectrodes 510 and 530 facing each other and an emissive layer 520 withtwo emitting parts disposed between the first and second electrodes 510and 530. The organic light emitting display device 100 (FIG. 1) includesa red pixel region, a green pixel region and a blue pixel region, andthe OLED D4 may be disposed in the blue pixel region. The firstelectrode 510 may be an anode and the second electrode 530 may be acathode.

The emissive layer 520 includes a first emitting part 620 that includesa first EML (EML1) 640 and a second emitting part 720 that includes asecond EML (EML2) 740. Also, the emissive layer 520 may further comprisea charge generation layer (CGL) 680 disposed between the first emittingpart 620 and the second emitting part 720.

The CGL 680 is disposed between the first and second emitting parts 620and 720 so that the first emitting part 620, the CGL 680 and the secondemitting part 720 are sequentially disposed on the first electrode 510.In other words, the first emitting part 620 is disposed between thefirst electrode 510 and the CGL 680 and the second emitting part 720 isdisposed between the second electrode 530 and the CGL 680.

The first emitting part 620 comprises the EML1 640. The first emittingpart 620 may further comprise at least one of an HIL 650 disposedbetween the first electrode 510 and the EML1 640, a first HTL (HTL1) 660disposed between the HIL 650 and the EML 640 and a first ETL (ETL1) 670disposed between the EML1 640 and the CGL 680. Alternatively, the firstemitting part 620 may further comprise a first EBL (EBL1) 665 disposedbetween the HTL1 660 and the EML1 640 and/or a first HBL (HBL1) 675disposed between the EML1 640 and the ETL1 670.

The second emitting part 720 comprises the EML2 740. The second emittingpart 720 may further comprise at least one of a second HTL (HTL2) 760disposed between the CGL 680 and the EML2 740, a second ETL (ETL2) 770disposed between the EML2 740 and the second electrode 530 and an EIL780 disposed between the ETL2 770 and the second electrode 530.Alternatively, the second emitting part 720 may further comprise asecond EBL (EBL2) 765 disposed between the HTL2 760 and the EML2 740and/or a second HBL (HBL2) 775 disposed between the EML2 740 and theETL2 770.

The CGL 680 is disposed between the first emitting part 620 and thesecond emitting part 720. The first emitting part 620 and the secondemitting part 720 are connected via the CGL 680. The CGL 680 may be aPN-junction CGL that junctions an N-type CGL (N-CGL) 682 with a P-typeCGL (P-CGL) 684.

The N-CGL 682 is disposed between the ETL1 670 and the HTL2 760 and theP-CGL 684 is disposed between the N-CGL 682 and the HTL2 760. The N-CGL682 transports electrons to the EML1 640 of the first emitting part 620and the P-CGL 684 transport holes to the EML2 740 of the second emittingpart 720.

In this aspect, each of the EML1 640 and the EML2 740 may be a blueemitting material layer. For example, at least one of the EML1 640 andthe EML2 740 comprise the first compound DF of the delayed fluorescentmaterial, the second compound FD of the fluorescent material, andoptionally the third compound H of the host.

As an example, when the EML1 640 includes the first to third compounds,the contents of the third compound H may be larger than or equal to thecontents of the first compound DF, and the contents of the firstcompound DF is larger than the contents of the second compound FD. Inthis case, exciton energy can be transferred efficiently from the firstcompound DF to the second compound FD. As an example, the EML1 640 maycomprise, but is not limited to, the third compound H between about 65wt % and about 90 wt %, the first compound DF between about 5 wt % andabout 30 wt % and the second compound FD between about 0.1 wt % andabout 5 wt %, respectively.

In one exemplary aspect, the EML2 740 may comprise the first and secondcompounds DF and FD, and optionally the first compound H as the same theEML1 640. Alternatively, the EML2 740 may include another compound thatis different from at least one of the first compound DF and the secondcompound FD in the EML1 640, and thus the EML2 740 may emit lightdifferent from the light emitted from the EML1 640 or may have differentluminous efficiency different from the luminous efficiency of the EML1640.

In FIG. 14, each of the EML1 640 and the EML2 740 has a single-layeredstructure. Alternatively, each of the EML1 640 and the EML2 740, each ofwhich may include the first to third compounds, may have adouble-layered structure (FIG. 8) or a triple-layered structure (FIG.11), respectively.

In the OLED D4, the singlet exciton energy of the first compound DF ofthe delayed fluorescent material is transferred to the second compoundFD of fluorescent material, and the final emission is occurred at thesecond compound FD. Accordingly, the OLED D4 can have excellent luminousefficiency and color purity. In addition, the OLED D4 includes at leastone EML including the first compound DF having the structure of Formulae1 to 3 and the second compound FD having the structure of Formulae 4 to6 so that the OLED D4 can enhance further its luminous efficiency andcolor purity. Moreover, since the OLED D4 has a double stack structureof a blue emitting material layer, the OLEO D4 can improve its colorsense or optimize its luminous efficiency.

FIG. 15 is a schematic cross-sectional view illustrating an organiclight emitting display device in accordance with another exemplaryaspect of the present disclosure. As illustrated in FIG. 15, an organiclight emitting display device 800 includes a substrate 810 that definesfirst to third pixel regions P1, P2 and P3, a thin film transistor Trdisposed over the substrate 810 and an OLED D disposed over the thinfilm transistor Tr and connected to the thin film transistor Tr. As anexample, the first pixel region P1 may be a blue pixel region, thesecond pixel region P2 may be a green pixel region and the third pixelregion P3 may be a red pixel region.

The substrate 810 may be a glass substrate or a flexible substrate. Forexample, the flexible substrate may be any one of a PI substrate, a PESsubstrate, a PEN substrate, a PET substrate and a PC substrate.

A buffer layer 812 is disposed over the substrate 810 and the thin filmtransistor Tr is disposed over the buffer layer 812. The buffer layer812 may be omitted. As illustrated in FIG. 2, the thin film transistorTr includes a semiconductor layer, a gate electrode, a source electrodeand a drain electrode and acts as a driving element.

A passivation layer 850 is disposed over the thin film transistor Tr.The passivation layer 850 has a flat top surface and a drain contacthole 852 that exposes a drain electrode of the thin film transistor Tr.

The OLED D is disposed over the passivation layer 850, and includes afirst electrode 910 that is connected to the drain electrode of the thinfilm transistor Tr, and an emissive layer 920 and a second electrode 930each of which is disposed sequentially on the first electrode 910. TheOLED D is disposed in each of the first to third pixel regions P1, P2and P3 and emits different light in each pixel region. For example, theOLED D in the first pixel region P1 may emit blue light, the OLED D inthe second pixel region P2 may emit green light and the OLED D in thethird pixel region P3 may emit red light.

The first electrode 910 is separately formed for each of the first tothird pixel regions P1, P2 and P3, and the second electrode 930corresponds to the first to third pixel regions P1, P2 and P3 and isformed integrally.

The first electrode 910 may be one of an anode and a cathode, and thesecond electrode 930 may be the other of the anode and the cathode. Inaddition, one of the first electrode 910 and the second electrode 930 isa transmissive (or semi-transmissive) electrode and the other of thefirst electrode 910 and the second electrode 930 is a reflectiveelectrode.

For example, the first electrode 910 may be an anode and may includeconductive material having a relatively high work function value, i.e.,a transparent conductive oxide layer of transparent conductive oxide(TCO). The second electrode 930 may be a cathode and may includeconductive material having relatively low work function value, i.e., ametal material layer of low-resistant metal. For example, the firstelectrode 910 may include any one of ITO, IZO, ITZO, SnO, ZnO, ICO andAZO, and the second electrode 930 may include Al, Mg, Ca, Ag, alloythereof (e.g. Mg—Ag) or combination thereof.

When the organic light emitting display device 800 is a bottom-emissiontype, the first electrode 910 may have a single-layered structure of atransparent conductive oxide layer.

Alternatively, when the organic light emitting display device 800 is atop-emission type, a reflective electrode or a reflective layer may bedisposed under the first electrode 910. For example, the reflectiveelectrode or the reflective layer may include, but is not limited to, Agor APC alloy. In the OLED D of the top-emission type, the firstelectrode 910 may have a triple-layered structure of ITO/Ag/ITO orITO/APC/ITO. Also, the second electrode 930 is thin so as to havelight-transmissive (or semi-transmissive) property.

A bank layer 860 is disposed on the passivation layer 850 in order tocover edges of the first electrode 910. The bank layer 860 correspondsto each of the first to third pixel regions P1, P2 and P3 and exposes acenter of the first electrode 910.

An emissive layer 920 is disposed on the first electrode 910. In oneexemplary aspect, the emissive layer 920 may have a single-layeredstructure of an EML. Alternatively, the emissive layer 920 may includeat least one of a HIL, a HTL, and an EBL disposed sequentially betweenthe first electrode 910 and the EML and/or a HBL, an ETL and an EILdisposed sequentially between the EML and the second electrode 930.

In one exemplary aspect, the EML of the emissive layer 930 in the firstpixel region P1 of the blue pixel region may comprise the first compoundDF of the delayed fluorescent material having the structure of Formulae1 to 3, the second compound FD of the boron-based fluorescent materialhaving the structure of Formula 4 to 6, and optionally the thirdcompound H of the host.

An encapsulation film 870 is disposed over the second electrode 930 inorder to prevent outer moisture from penetrating into the OLED D. Theencapsulation film 870 may have, but is not limited to, a triple-layeredstructure of a first inorganic insulating film, an organic insulatingfilm and a second inorganic insulating film.

The organic light emitting display device 800 may have a polarizer inorder to decrease external light reflection. For example, the polarizermay be a circular polarizer. When the organic light emitting displaydevice 800 is a bottom-emission type, the polarizer may be disposedunder the substrate 810. Alternatively, when the organic light emittingdisplay device 800 is a top emission type, the polarizer may be disposedover the encapsulation film 870.

FIG. 16 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure. As illustrated in FIG. 16, the OLED D5 comprises a firstelectrode 910, a second electrode 930 facing the first electrode 910 andan emissive layer 920 disposed between the first and second electrodes910 and 930.

The first electrode 910 may be an anode and the second electrode 930 maybe a cathode. As an example, the first electrode 910 may be a reflectiveelectrode and the second electrode 930 may be a transmissive (orsemi-transmissive) electrode.

The emissive layer 920 comprises an EML 940. The emissive layer 930 maycomprise at least one of an HTL 960 disposed between the first electrode910 and the EML 940 and an ETL 970 disposed between the EML 940 and thesecond electrode 930. Also, the emissive layer 920 may further compriseat least one of an HIL 950 disposed between the first electrode 910 andthe HTL 960 and an EIL 980 disposed between the ETL 970 and the secondelectrode 930. In addition, the emissive layer 920 may further compriseat least one of an EBL 965 disposed between the HTL 960 and the EML 940and an HBL 975 disposed between the EML 940 and the ETL 970.

In addition, the emissive layer 920 may further comprise an auxiliaryhole transport layer (auxiliary HTL) 962 disposed between the HTL 960and the EBL 965. The auxiliary HTL 962 may comprise a first auxiliaryHTL 962 a located in the first pixel region P1, a second auxiliary HTL962 b located in the second pixel region P2 and a third auxiliary HTL962 c located in the third pixel region P3.

The first auxiliary HTL 962 a has a first thickness, the secondauxiliary HTL 962 b has a second thickness and the third auxiliary HTL962 c has a third thickness. The first thickness is less than the secondthickness and the second thickness is less than the third thickness.Accordingly, the OLED D5 has a micro-cavity structure.

Owing to the first to third auxiliary HTLs 962 a, 962 b and 962 c havingdifferent thickness to each other, the distance between the firstelectrode 910 and the second electrode 930 in the first pixel region P1emitting light in the first wavelength range (blue light) is smallerthan the distance between the first electrode 910 and the secondelectrode 930 in the second pixel region P2 emitting light in the secondwavelength range (green light), which is longer than the first wavelength range. Also, the distance between the first electrode 910 and thesecond electrode 930 in the first pixel region P2 is smaller than thedistance between the first electrode 910 and the second electrode 930 inthe third pixel region P3 emitting light in the third wavelength range(red light), which is longer than the second wavelength range.Accordingly, the OLED D5 has improved luminous efficiency.

In FIG. 16, the first auxiliary HTL 962 a is located in the third pixelregion P1. Alternatively, the OLED D5 may implement the micro-cavitystructure without the first auxiliary HTL 962 a. In addition, a cappinglayer 880 may be disposed over the second electrode 930 in order toimprove out-coupling of the light emitted from the OLED D5.

The EML 940 comprises a first EML (EML1) 942 located in the first pixelregion P1, a second EML (EML2) 944 located in the second pixel region P2and a third EML (EML3) 946 located in the third pixel region P3. Each ofthe EML1 942, the EML2 944 and the EML3 946 may be a blue EML, a greenEML and a red EML, respectively.

In one exemplary aspect, the EML1 942 located in the first pixel regionP1 may comprise the first compound DF of the delayed fluorescentmaterial having the structure of Formulae 1 to 3, the second compound FDof the boron-based fluorescent material having the structure of Formulae4 to 6, and optionally the third compound H of the host. The EML1 942may have a single-layered structure, a double-layered structure (FIG. 8)or a triple-layered structure (FIG. 11).

When the EML1 942 includes the first to third compounds DF, FD and H,the contents of the third compound H may be larger than or equal to thecontents of the first compound DF, and the contents of the firstcompound DF is larger than the contents of the second compound FD. Inthis case, exciton energy can be transferred efficiently from the firstcompound DF to the second compound FD. As an example, the EML1 942 maycomprise, but is not limited to, the third compound H between about 65wt % and about 90 wt %, the first compound DF between about 5 wt % andabout 30 wt %, and the second compound FD between about 0.1 wt % andabout 5 wt %, respectively.

The EML2 944 located in the second pixel region P2 may comprise a hostand green dopant and the EML3 946 located in the third pixel region P3may comprise a host and red dopant. For example, the host in the EML2944 and the EML3 946 may comprise the third compound H, and each of thegreen dopant and the red dopant may comprise at least one of green orred phosphorescent material, green or red fluorescent material and greenor red delayed fluorescent material.

The OLED D5 emits blue light, green light and red light in each of thefirst to third pixel regions P1, P2 and P3 so that the organic lightemitting display device 800 (FIG. 15) may implement a full-color image.

The organic light emitting display device 800 may further comprise acolor filter layer corresponding to the first to third pixel regions P1,P2 and P3 for improving color purity of the light emitted from the OLEDD. As an example, the color filter layer may comprise a first colorfilter layer (blue color filter layer) corresponding to the first pixelregion P1, the second color filter layer (green color filter layer)corresponding to the second pixel region P2 and the third color filterlayer (red color filter layer) corresponding to the third pixel regionP3.

When the organic light emitting display device 800 is a bottom-emissiontype, the color filter layer may be disposed between the OLED D and thesubstrate 810. Alternatively, when the organic light emitting displaydevice 800 is a top-emission type, the color filter layer may bedisposed over the OLED D.

FIG. 17 is a schematic cross-sectional view illustrating an organiclight emitting display device in accordance with still another exemplaryaspect of the present disclosure. As illustrated in FIG. 17, the organiclight emitting display device 1000 comprise a substrate 1010 defining afirst pixel region P1, a second pixel region P2 and a third pixel regionP3, a thin film transistor Tr disposed over the substrate 1010, an OLEDD disposed over the thin film transistor Tr and connected to the thinfilm transistor Tr and a color filter layer 1020 corresponding to thefirst to third pixel regions P1, P2 and P3. As an example, the firstpixel region P1 may be a blue pixel region, the second pixel region P2may be a green pixel region and the third pixel region P3 may be a redpixel region.

The substrate 1010 may be a glass substrate or a flexible substrate. Forexample, the flexible substrate may be any one of a PI substrate, a PESsubstrate, a PEN substrate, a PET substrate and a PC substrate. The thinfilm transistor Tr is located over the substrate 1010. Alternatively, abuffer layer may be disposed over the substrate 1010 and the thin filmtransistor Tr may be disposed over the buffer layer. As illustrated inFIG. 2, the thin film transistor Tr includes a semiconductor layer, agate electrode, a source electrode and a drain electrode and acts as adriving element.

The color filter layer 1020 is located over the substrate 1010. As anexample, the color filter layer 1020 may comprise a first color filterlayer 1022 corresponding to the first pixel region P1, a second colorfilter layer 1024 corresponding to the second pixel region P2 and athird color filter layer 1026 corresponding to the third pixel regionP3. The first color filter layer 1022 may be a blue color filter layer,the second color filter layer 1024 may be a green color filter layer andthe third color filter layer 1026 may be a red color filter layer. Forexample, the first color filter layer 1022 may comprise at least one ofblue dye or green pigment, the second color filter layer 1024 maycomprise at least one of green dye or red pigment and the third colorfilter layer 1026 may comprise at least one of red dye or blue pigment.

A passivation layer 1050 is disposed over the thin film transistor Trand the color filter layer 1020. The passivation layer 1050 has a flattop surface and a drain contact hole 1052 that exposes a drain electrodeof the thin film transistor Tr.

The OLED D is disposed over the passivation layer 1050 and correspondsto the color filter layer 1020. The OLED D includes a first electrode1110 that is connected to the drain electrode of the thin filmtransistor Tr, and an emissive layer 1120 and a second electrode 1130each of which is disposed sequentially on the first electrode 1110. TheOLED D emits white light in the first to third pixel regions P1, P2 andP3.

The first electrode 1110 is separately formed for each of the first tothird pixel regions P1, P2 and P3, and the second electrode 1130corresponds to the first to third pixel regions P1, P2 and P3 and isformed integrally.

The first electrode 1110 may be one of an anode and a cathode, and thesecond electrode 1130 may be the other of the anode and the cathode. Inaddition, the first electrode 1110 may be a transmissive (orsemi-transmissive) electrode and the second electrode 1130 may be areflective electrode.

For example, the first electrode 1110 may be an anode and may includeconductive material having a relatively high work function value, i.e.,a transparent conductive oxide layer of transparent conductive oxide(TCO). The second electrode 1130 may be a cathode and may includeconductive material having relatively low work function value, i.e., ametal material layer of low-resistant metal. For example, thetransparent conductive oxide layer of the first electrode 1110 mayinclude any one of ITO, IZO, ITZO, SnO, ZnO, ICO and AZO, and the secondelectrode 1130 may include Al, Mg, Ca, Ag, alloy thereof (e.g., Mg—Ag)or combination thereof.

The emissive layer 1120 is disposed on the first electrode 1110. Theemissive layer 1120 includes at least two emitting parts emittingdifferent colors. Each of the emitting part may have a single-layeredstructure of an EML. Alternatively, each of the emitting parts mayinclude at least one of a HIL, a HTL, and an EBL, a HBL, an ETL and anEIL. In addition, the emissive layer 1120 may further comprise a CGLdisposed between the emitting parts.

At least one of the at least two emitting parts may comprise the firstcompound DF of the delayed fluorescent material having the structure ofFormulae 1 to 3, the second compound FD of the boron-based fluorescentmaterial having the structure of Formulae 4 to 6, and optionally thethird compound H of the host.

A bank layer 1060 is disposed on passivation layer 1050 in order tocover edges of the first electrode 1110. The bank layer 1060 correspondsto each of the first to third pixel regions P1, P2 and P3 and exposes acenter of the first electrode 1110. As described above, since the OLED Demits white light in the first to third pixel regions P1, P2 and P3, theemissive layer 1120 may be formed as a common layer without beingseparated in the first to third pixel regions P1, P2 and P3. The banklayer 1060 is formed to prevent current leakage from the edges of thefirst electrode 1110, and the bank layer 1060 may be omitted.

Moreover, the organic light emitting display device 1000 may furthercomprise an encapsulation film disposed on the second electrode 1130 inorder to prevent outer moisture from penetrating into the OLED D. Inaddition, the organic light emitting display device 1000 may furthercomprise a polarizer disposed under the substrate 1010 in order todecrease external light reflection.

In the organic light emitting display device 1000 in FIG. 17, the firstelectrode 1110 is a transmissive electrode, the second electrode 1130 isa reflective electrode, and the color filter layer 1020 is disposedbetween the substrate 1010 and the OLED D. That is, the organic lightemitting display device 1000 is a bottom-emission type. Alternatively,the first electrode 1110 may be a reflective electrode, the secondelectrode 1120 may be a transmissive electrode (or semi-transmissiveelectrode) and the color filter layer 1020 may be disposed over the OLEDD in the organic light emitting display device 1000.

In the organic light emitting display device 1000, the OLED D located inthe first to third pixel regions P1, P2 and P3 emits white light, andthe white light passes through each of the first to third pixel regionsP1, P2 and P3 so that each of a blue color, a green color and a redcolor is displayed in the first to third pixel regions P1, P2 and P3,respectively.

A color conversion film may be disposed between the OLED D and the colorfilter layer 1020. The color conversion film corresponds to the first tothird pixel regions P1, P2 and P3, and comprises a blue color conversionfilm, a green color conversion film and a red color conversion film eachof which can convert the white light emitted from the OLED D into bluelight, green light and red light, respectively. For example, the colorconversion film may comprise quantum dots. Accordingly, the organiclight emitting display device 1000 may further enhance its color purity.Alternatively, the color conversion film may displace the color filterlayer 1020.

FIG. 18 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure. As illustrated in FIG. 18, the OLED D6 comprises first andsecond electrodes 1110 and 1120 facing each other and an emissive layer1120 disposed between the first and second electrodes 1110 and 1120. Thefirst electrode 1110 may be an anode and the second electrode 1120 maybe a cathode. For example, the first electrode 1100 may be atransmissive electrode and the second electrode 1120 may be a reflectiveelectrode.

The emissive layer 1120 includes a first emitting part 1220 comprising afirst EML (EML1) 1240, a second emitting part 1320 comprising a secondEML (EML2) 1340 and a third emitting part 1420 comprising a third EML(EML3) 1440. In addition, the emissive layer 1120 may further comprise afirst charge generation layer (CGL1) 1280 disposed between the firstemitting part 1220 and the second emitting part 1320 and a second chargegeneration layer (CGL2) 1380 disposed between the second emitting part1320 and the third emitting part 1420. Accordingly, the first emittingpart 1220, the CGL1 1280, the second emitting part 1320, the CGL2 1380and the third emitting part 1420 are disposed sequentially on the firstelectrode 1110.

The first emitting part 1220 may further comprise at least one of an HIL1250 disposed between the first electrode 1110 and the EML1 1240, afirst HTL (HTL1) 1260 disposed between the EML1 1240 and the HIL 1250and a first ETL (ETL1) 1270 disposed between the EML1 1240 and the CGL11280. Alternatively, the first emitting part 1220 may further compriseat least one of a first EBL (EBL1) 1265 disposed between the HTL1 1260and the EML1 1240 and a first HBL (HBL1) 1275 disposed between the EML11240 and the ETL1 1270.

The second emitting part 1320 may further comprise at least one of asecond HTL (HTL2) 1360 disposed between the CGL1 1280 and the EML2 1340,a second ETL (ETL2) 1370 disposed between the EML2 1340 and the CGL21380. Alternatively, the second emitting part 1320 may further comprisea second EBL (EBL2) 1365 disposed between the HTL2 1360 and the EML21340 and/or a second HBL (HBL2) 1375 disposed between the EML2 1340 andthe ETL2 1370.

The third emitting part 1420 may further comprise at least one of athird HTL (HTL3) 1460 disposed between the CGL2 1380 and the EML3 1440,a third ETL (ETL3) 1470 disposed between the EML3 1440 and the secondelectrode 1130 and an EIL 1480 disposed between the ETL3 1470 and thesecond electrode 1130. Alternatively, the third emitting part 1420 mayfurther comprise a third EBL (EBL3) 1465 disposed between the HTL3 1460and the EML3 1440 and/or a third HBL (HBL3) 1475 disposed between theEML3 1440 and the ETL3 1470.

The CGL1 1280 is disposed between the first emitting part 1220 and thesecond emitting part 1320. That is, the first emitting part 1220 and thesecond emitting part 1320 are connected via the CGL1 1280. The CGL1 1280may be a PN-junction CGL that junctions a first N-type CGL (N-CGL1) 1282with a first P-type CGL (P-CGL1) 1284.

The N-CGL1 1282 is disposed between the ETL1 1270 and the HTL2 1360 andthe P-CGL1 1284 is disposed between the N-CGL1 1282 and the HTL2 1360.The N-CGL1 1282 transports electrons to the EML1 1240 of the firstemitting part 1220 and the P-CGL1 1284 transport holes to the EML2 1340of the second emitting part 1320.

The CGL2 1380 is disposed between the second emitting part 1320 and thethird emitting part 1420. That is, the second emitting part 1320 and thethird emitting part 1420 are connected via the CGL2 1380. The CGL2 1380may be a PN-junction CGL that junctions a second N-type CGL (N-CGL2)1382 with a second P-type CGL (P-CGL2) 1384.

The N-CGL2 1382 is disposed between the ETL2 1370 and the HTL3 1460 andthe P-CGL2 1384 is disposed between the N-CGL2 1382 and the HTL3 1460.The N-CGL2 1382 transports electrons to the EML2 1340 of the secondemitting part 1320 and the P-CGL2 1384 transport holes to the EML3 1440of the third emitting part 1420.

In this aspect, one of the first to third EMLs 1240, 1340 and 1440 maybe a blue EML, another of the first to third EMLs 1240, 1340 and 1440may be a green EML and the third of the first to third EMLs 1240, 1340and 1440 may be a red EML.

As an example, the EML1 1240 may be a blue EML, the EML2 1340 may be agreen EML and the EML3 1440 may be a red EML. Alternatively, the EML11240 may be a red EML, the EML2 1340 may be a green EML and the EML31440 may be a blue EML1.

Hereinafter, the OLED D6 where the EML1 1240 is the blue EML, the EML2is the green EML and the EML3 is the red EML will be described.

The EML1 1240 may comprise the first compound DF of the delayedfluorescent material having the structure of Formulae 1 to 3, the secondcompound FD of the boron-based fluorescent material having the structureof Formulae 4 to 6, and optionally the third compound H of the host. TheEML1 1240 may have a single-layered structure, a double-layeredstructure (FIG. 8) or a triple-layered structure (FIG. 11).

In the EML1 1240, the contents of the third compound H may be largerthan or equal to the contents of the first compound DF, and the contentsof the first compound DF is larger than the contents of the secondcompound FD. In this case, exciton energy can be transferred efficientlyfrom the first compound DF to the second compound FD. As an example, theEML1 1240 may comprise, but is not limited to, the third compound Hbetween about 65 wt % and about 90 wt %, the first compound DF betweenabout 5 wt % and about 30 wt %, and the second compound FD between about0.1 wt % and about 5 wt %, respectively.

The EML2 1340 may include a host and a green dopant and the EML3 1400may include a host and a red dopant. As an example, the host in the EML21340 and the EML3 1440 may comprise the third compound H, and each ofthe green dopant and the red dopant may comprise at least one of greenor red phosphorescent material, green or red fluorescent material andgreen or red delayed fluorescent material.

The OLED D6 emits white light in each of the first to third pixelregions P1, P2 and P3 and the white light passes though the color filterlayer 1020 (FIG. 17) correspondingly disposed in the first to thirdpixel regions P1, P2 and P3. Accordingly, the organic light emittingdisplay device 1000 (FIG. 17) can implement a full-color image.

FIG. 19 is a schematic cross-sectional view illustrating an OLED inaccordance with still another exemplary aspect of the presentdisclosure. As illustrated in FIG. 19, the OLED D7 comprises first andsecond electrodes 1110 and 1120 facing each other and an emissive layer1120A disposed between the first and second electrodes 1110 and 1120.The first electrode 1110 may be an anode and the second electrode 1120may be a cathode. For example, the first electrode 1100 may be atransmissive electrode and the second electrode 1120 may be a reflectiveelectrode.

The emissive layer 1120A includes a first emitting part 1520 comprisingan EML1 1540, a second emitting part 1620 comprising an EML2 1640 and athird emitting part 1720 comprising a EML3 1740. In addition, theemissive layer 1120A may further comprise a CGL1 1580 disposed betweenthe first emitting part 1520 and the second emitting part 1620 and aCGL2 1680 disposed between the second emitting part 1620 and the thirdemitting part 1720. Accordingly, the first emitting part 1520, the CGL11580, the second emitting part 1620, the CGL2 1680 and the thirdemitting part 1720 are disposed sequentially on the first electrode1110.

The first emitting part 1520 may further comprise at least one of an HIL1550 disposed between the first electrode and the EML1 1540, an HTL11560 disposed between the EML1 1540 and the HIL 1550 and an ETL1 1570disposed between the EML1 1540 and the CGL1 1580. Alternatively, thefirst emitting part 1520 may further comprise an EBL1 1565 disposedbetween the HTL1 1560 and the EML1 1540 and/or a HBL1 1575 disposedbetween the EML1 1540 and the ETL1 1570.

The EML2 1640 of the second emitting part 1620 comprises a lower EML1642 and an upper EML 1644. The lower EML 1642 is located adjacently tothe first electrode 1110 and the upper EML 1644 is located adjacently tothe second electrode 1130. In addition, the second emitting part 1620may further comprise at least one of an HTL2 1660 disposed between theCGL1 1580 and the EML2 1640, an ETL2 1670 disposed between the EML2 1640and the CGL2 1680. Alternatively, the second emitting part 1620 mayfurther comprise at least one of an EBL2 1665 disposed between the HTL21660 and the EML2 1640 and an HBL2 1675 disposed between the EML2 1640and the ETL2 1670.

The third emitting part 1720 may further comprise at least one of anHTL3 1760 disposed between the CGL2 1680 and the EML3 1740, an ETL3 1770disposed between the EML3 1740 and the second electrode 1130 and an EIL1780 disposed between the ETL3 1770 and the second electrode 1130.Alternatively, the third emitting part 1720 may further comprise an EBL31765 disposed between the HTL3 1760 and the EML3 1740 and/or a HBL3 1775disposed between the EML3 1740 and the ETL3 1770.

The CGL1 1580 is disposed between the first emitting part 1520 and thesecond emitting part 1620. That is, the first emitting part 1520 and thesecond emitting part 1620 are connected via the CGL1 1580. The CGL1 1580may be a PN-junction CGL that junctions an N-CGL1 1582 with a P-CGL11584. The N-CGL1 1582 is disposed between the ETL1 1570 and the HTL21660 and the P-CGL1 1584 is disposed between the N-CGL1 1582 and theHTL2 1560.

The CGL2 1680 is disposed between the second emitting part 1620 and thethird emitting part 1720. That is, the second emitting part 1620 and thethird emitting part 1720 are connected via the CGL2 1680. The CGL2 1680may be a PN-junction CGL that junctions an N-CGL2 1682 with a P-CGL21684. The N-CGL2 1682 is disposed between the ETL2 1570 and the HTL31760 and the P-CGL2 1684 is disposed between the N-CGL2 1682 and theHTL3 1760. In one exemplary aspect, at least one of the N-CGL1 1582 andthe N-CGL2 1682 may include any organic compound having the structure ofChemical Formulae 1 to 3.

In this aspect, each of the EML1 1540 and the EML3 1740 may be a blueEML. In an exemplary aspect, each of the EML1 1540 and the EML3 1740 maycomprise the first compound DF of the delayed fluorescent material, thesecond compound FD of the boron-based fluorescent material, andoptionally the third compound H of the host. Each of the first to thirdcompounds DF, FD and H in the EML1 1540 may be identical to or differentfrom each of the first to third compounds DF, FD and H in the EML3 1740,respectively. Alternatively, the EML3 1740 may include another compoundthat is different from at least one of the first compound DF and thesecond compound FD in the EML1 1540, and thus the EML2 1740 may emitlight different from the light emitted from the EML1 1540 or may havedifferent luminous efficiency different from the luminous efficiency ofthe EML1 1540.

As an example, when the EML1 1540 and the EML3 1740 include the first tothird compounds DF, FD and H, the contents of the third compound H maybe larger than or equal to the contents of the first compound DF, andthe contents of the first compound DF is larger than the contents of thesecond compound FD in each of the EML1 1540 and the EML3 1740. In thiscase, exciton energy can be transferred efficiently from the firstcompound DF to the second compound FD. As an example, each of the EML11540 and the EML3 1740 may comprise, but is not limited to, the thirdcompound H between about 65 wt % and about 90 wt %, the first compoundDF between about 5 wt % and about 30 wt % and the second compound FDbetween about 0.1 wt % and about 5 wt %, respectively.

One of the lower EML 1642 and the upper EML 1644 in the EML2 1640 may bea green EML and the other of the lower EML 1642 and the upper EML 1644in the EML2 1640 may be a red EML. The green EML and the red EML issequentially disposed to form the EML2 1640.

In one exemplary aspect, the lower EML 1642 of the green EML maycomprise a host and a green dopant and the upper EML 1644 of the red EMLmay comprise a host and a red dopant. As an example, the host mayinclude the third compound H, and each of the green dopant and the reddopant may comprise at least one of green or red phosphorescentmaterial, green or red fluorescent material and green or red delayedfluorescent material.

The OLED D7 emits white light in each of the first to third pixelregions P1, P2 and P3 and the white light passes though the color filterlayer 1020 (FIG. 17) correspondingly disposed in the first to thirdpixel regions P1, P2 and P3. Accordingly, the organic light emittingdisplay device 1000 (FIG. 17) can implement a full-color image.

In FIG. 19, the OLED D7 has a three-stack structure including the firstto three emitting parts 1520, 1620 and 1720 which includes the EML1 1540and the EML3 1740 as a blue EML. Alternatively, the OLED D7 may have atwo-stack structure where one of the first emitting part 1520 and thethird emitting part 1720 each of which includes the EML1 1540 and theEML3 1740 as a blue EML is omitted.

Example 1 (Ex. 1): Fabrication of OLED

An OLED comprising an EML into which Compound 1-1 of Formula 3 (HOMO:−5.6 eV, LUMO: −2.7 eV) as the first compound DF, Compound 2-1 ofFormula 6 (HOMO: −5.6 eV, LUMO: −2.9 eV) as the second compound FD andmCBP (HOMO: −6.0 eV, LUMO: −2.5 eV) was introduced was fabricated. ITOsubstrate was washed by UV-Ozone treatment before using, and wastransferred to a vacuum chamber for depositing emission layer.Subsequently, an anode, an emission layer and a cathode were depositedby evaporation from a heating boat under 10⁻⁷ torr vacuum condition withsetting deposition rate of 1 Å/s in the following order:

An anode (ITO, 50 nm); an HIL (HAT-CN, 7 nm); an HTL (NPB, 45 nm); anEBL (TAPC, 10 nm), an EML (mCBP (89 wt %), Compound 1-1 (10 wt %) andCompound 2-1 (1 wt %), 35 nm); an HBL (B3PYMPM, 10 nm); an ETL (TPBi, 25nm), an EIL (LiF); and a cathode (Al).

Example 2 (Ex. 2): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-2 (HOMO: −5.5 eV, LUMO: −2.6 eV) of Formula 3 as thefirst compound instead of Compound 1-1 was used in the EML.

Example 3 (Ex. 3): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 2-2 (HOMO: −5.4 eV, LUMO: −2.8 eV) of Formula 6 as thesecond compound instead of Compound 2-1 was used in the EML.

Example 4 (Ex. 4): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-2 (HOMO: −5.5 eV, LUMO: −2.6 eV) of Formula 3 as thefirst compound instead of Compound 1-1 and Compound 2-2 (HOMO: −5.4 eV,LUMO: −2.8 eV) of Formula 6 as the second compound instead of Compound2-1 were used in the EML.

Example 5 (Ex. 5): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-2 (HOMO: −5.5 eV, LUMO: −2.6 eV) of Formula 3 as thefirst compound instead of Compound 1-1 and Compound 2-3 (HOMO: −5.4 eV,LUMO: −2.8 eV) of Formula 6 as the second compound instead of Compound2-1 were used in the EML.

Example 6 (Ex. 6): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-2 (HOMO: −5.5 eV, LUMO: −2.6 eV) of Formula 3 as thefirst compound instead of Compound 1-1 and Compound 2-9 (HOMO: −5.5 eV,LUMO: −2.9 eV) of Formula 6 as the second compound instead of Compound2-1 were used in the EML.

Example 7 (Ex. 7): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-3 (HOMO: −5.5 eV, LUMO: −2.6 eV) of Formula 3 as thefirst compound instead of Compound 1-1 and Compound 2-2 (HOMO: −5.4 eV,LUMO: −2.8 eV) of Formula 6 as the second compound instead of Compound2-1 were used in the EML.

Example 8 (Ex. 8): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-4 (HOMO: −5.4 eV, LUMO: −2.6 eV) of Formula 3 as thefirst compound instead of Compound 1-1 was used in the EML.

Example 9 (Ex. 9): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-4 (HOMO: −5.4 eV, LUMO: −2.6 eV) of Formula 3 as thefirst compound instead of Compound 1-1 and Compound 2-2 (HOMO: −5.4 eV,LUMO: −2.8 eV) of Formula 6 as the second compound instead of Compound2-1 were used in the EML.

Example 10 (Ex. 10): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-5 (HOMO: −5.6 eV, LUMO: −2.5 eV) of Formula 3 as thefirst compound instead of Compound 1-1 was used in the EML.

Example 11 (Ex. 11): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-5 (HOMO: −5.6 eV, LUMO: −2.5 eV) of Formula 3 as thefirst compound instead of Compound 1-1 and Compound 2-2 (HOMO: −5.4 eV,LUMO: −2.8 eV) of Formula 6 as the second compound instead of Compound2-1 were used in the EML.

Comparative Example 1 (Ref. 1): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref 2-1 (HOMO: −5.2 eV, LUMO: −2.7 eV) as the secondcompound instead of Compound 2-1 was used in the EML.

Comparative Example 2 (Ref. 2): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref 2-2 (HOMO: −5.2 eV, LUMO: −2.6 eV) as the secondcompound instead of Compound 2-1 was used in the EML.

Comparative Example 3 (Ref. 3): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-2 of Formula 3 as the first compound instead of Compound1-1 and the following Ref 2-1 (HOMO: −5.2 eV, LUMO: −2.7 eV) as thesecond compound instead of Compound 2-1 were used in the EML.

Comparative Example 4 (Ref. 4): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-2 of Formula 3 as the first compound instead of Compound1-1 and the following Ref 2-2 (HOMO: −5.2 eV, LUMO: −2.6 eV) as thesecond compound instead of Compound 2-1 were used in the EML.

Comparative Example 5 (Ref. 5): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref. 1-1 (HOMO: −5.9 eV, LUMO: −2.8 eV) as the firstcompound instead of Compound 1-1 was used in the EML.

Comparative Example 6 (Ref. 6): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref. 1-1 (HOMO: −5.9 eV, LUMO: −2.8 eV) as the firstcompound instead of Compound 1-1 and Compound 2-2 as the second compoundinstead of Compound 2-1 were used in the EML.

Comparative Example 7 (Ref. 7): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref. 1-1 (HOMO: −5.9 eV, LUMO: −2.8 eV) as the firstcompound instead of Compound 1-1 and the following Ref 2-1 (HOMO: −5.2eV, LUMO: −2.7 eV) as the second compound instead of Compound 2-1 wereused in the EML.

Comparative Example 8 (Ref. 8): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref. 1-1 (HOMO: −5.9 eV, LUMO: −2.8 eV) as the firstcompound instead of Compound 1-1 and the following Ref 2-2 (HOMO: −5.2eV, LUMO: −2.6 eV) as the second compound instead of Compound 2-1 wereused in the EML.

Comparative Example 9 (Ref. 9): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref. 1-2 (HOMO: −6.0 eV, LUMO: −3.0 eV) as the firstcompound instead of Compound 1-1 was used in the EML.

Comparative Example 10 (Ref 10): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref. 1-2 (HOMO: −6.0 eV, LUMO: −3.0 eV) as the firstcompound instead of Compound 1-1 and the following Ref 2-1 (HOMO: −5.2eV, LUMO: −2.7 eV) as the second compound instead of Compound 2-1 wereused in the EML.

Comparative Example 11 (Ref 11): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref. 1-3 (HOMO: −5.9 eV, LUMO: −2.8 eV) as the firstcompound instead of Compound 1-1 and the following Ref 2-1 (HOMO: −5.2eV, LUMO: −2.7 eV) as the second compound instead of Compound 2-1 wereused in the EML.

Comparative Example 12 (Ref 12): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat the following Ref. 1-3 (HOMO: −5.9 eV, LUMO: −2.8 eV) as the firstcompound instead of Compound 1-1 and Compound 2-2 as the second compoundinstead of Compound 2-1 were used in the EML.

Comparative Example 13 (Ref 13): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-2 as the first compound instead of Compound 1-1 and thefollowing Ref. 2-3 (HOMO: −5.2 eV, LUMO: −2.5 eV) as the second compoundinstead of Compound 2-1 were used in the EML.

Comparative Example 14 (Ref 14): Fabrication of OLED

An OLED was fabricated using the same materials as Example 1, exceptthat Compound 1-5 as the first compound instead of Compound 1-1 and thefollowing Ref. 2-3 (HOMO: −5.2 eV, LUMO: −2.5 eV) as the second compoundinstead of Compound 2-1 were used in the EML.

The following table 1 indicates the kinds of the first and secondcompounds and the energy level bandgap (ΔHOMO) between the HOMO energylevel of the first compound and the second compound.

TABLE 1 First and Second Compounds in EML First Compound Second CompoundHOMO HOMO ΔHOMO Sample Material (eV) Material (eV) (eV) Ref. 1 1-1 −5.6Ref. 2-1 −5.2 0.4 Ref. 2 1-1 −5.6 Ref. 2-2 −5.2 0.4 Ref. 3 1-2 −5.5 Ref.2-1 −5.2 0.3 Ref. 4 1-2 −5.5 Ref. 2-2 −5.2 0.3 Ref. 5 Ref. 1-1 −5.9 2-1−5.6 0.3 Ref. 6 Ref. 1-1 −5.9 2-2 −5.4 0.5 Ref. 7 Ref. 1-1 −5.9 Ref. 2-1−5.2 0.7 Ref. 8 Ref. 1-1 −5.9 Ref. 2-2 −5.2 0.7 Ref. 9 Ref. 1-2 −6.0 2-1−5.6 0.4 Ref. 10 Ref. 1-2 −6.0 Ref. 2-1 −5.2 0.8 Ref. 11 Ref. 1-3 −5.9Ref. 2-1 −5.2 0.7 Ref. 12 Ref. 1-3 −5.9 2-2 −5.4 0.5 Ref. 13 1-2 −5.5Ref. 1-3 −5.2 0.3 Ref. 14 1-5 −5.6 Ref. 1-3 −5.2 0.4 Ex. 1 1-1 −5.6 2-1−5.6 0 Ex. 2 1-2 −5.5 2-1 −5.6 0.1 Ex. 3 1-1 −5.6 2-2 −5.4 0.2 Ex. 4 1-2−5.5 2-2 −5.4 0.1 Ex. 5 1-2 −5.5 2-3 −5.4 0.1 Ex. 6 1-2 −5.5 2-9 −5.5 0Ex. 7 1-3 −5.5 2-2 −5.4 0.1 Ex. 8 1-4 −5.4 2-1 −5.6 0.2 Ex. 9 1-4 −5.42-2 −5.4 0 Ex. 10 1-5 −5.6 2-1 −5.6 0 Ex. 11 1-5 −5.6 2-2 −5.4 0.2

Experimental Example 1: Measurement of Luminous Properties of OLED

Each of the OLED fabricated in Ex. 1-11 and Ref. 1-14 was connected toan external power source and then luminous properties for all the diodeswere evaluated using a constant current source (KEITHLEY) and aphotometer PR650 at room temperature. In particular, driving voltage(V), current efficiency (cd/A), power efficiency (lm/W), colorcoordinate and external quantum efficiency (EQE, %) at 8.6 mA/m² currentdensity as well as whether or not hole trap and exciplex formation weremeasured. The measurement results for the OLEDs are shown in thefollowing table 2 and FIGS. 20 and 21.

TABLE 2 Luminous Properties of OLED EQE Hole Exciplex Sample V cd/A lm/WCIEy (%) Trap Formation Ref. 1 5.58 7.3 6.6 0.104 8.2 Y N Ref. 2 4.409.7 7.4 0.165 7.5 Y N Ref. 3 5.36 14.2 8.0 0.184 10.2 Y N Ref. 4 4.1815.5 11.7 0.172 11.5 Y N Ref. 5 4.98 12.1 7.6 0.208 8.5 Y N Ref. 6 4.8712.3 8.4 0.216 10.8 Y N Ref. 7 3.53 16.4 10.7 0.417 9.4 Y Y Ref. 8 3.5724.5 21.0 0.336 10.7 Y Y Ref. 9 5.05 10.2 6.7 0.212 6.9 Y N Ref. 10 3.3517.1 13.5 0.405 8.3 Y Y Ref. 11 3.42 17.3 14.1 0.398 8.4 Y Y Ref. 123.66 25.6 22.0 0.221 11.9 Y N Ref. 13 4.68 12.6 10.6 0.115 9.8 Y N Ref.14 4.15 14.2 11.1 0.116 10.6 Y N Ex. 1 3.95 35.5 29.7 0.198 15.2 N N Ex.2 3.41 42.3 35.2 0.195 17.3 N N Ex. 3 3.77 41.4 33.9 0.221 19.8 N N Ex.4 3.25 37.8 36.5 0.203 22.7 N N Ex. 5 3.28 35.7 32.8 0.215 19.9 N N Ex.6 3.40 32.2 29.3 0.211 17.1 N N Ex. 7 3.63 36.6 29.9 0.204 18.7 N N Ex.8 4.09 35.0 29.6 0.189 16.9 N N Ex. 9 4.01 37.3 36.0 0.202 21.6 N N Ex.10 3.68 34.3 31.1 0.191 17.8 N N Ex. 11 3.52 35.1 34.2 0.199 20.7 N N

As indicated in Table 2 and FIGS. 20 and 21, holes were trapped in theOLEDs fabricated in Comparative Examples each of which is designed tohave the HOMO energy level bandgap between the first and secondcompounds is equal to or more than 0.3 eV, and as a result, the drivingvoltages of the OLEDs were raised, electrical properties of the OLEDswere deteriorated, and FWHM of the OLEDs was increased due to excitonsthat were not transferred to the second compound from the firstcompound. Particularly, it was confirmed that exciplex was formedbetween the LUMO of the first compound and the HOMO of the secondcompound in the OLEDs each of which is designed to have the HOMO energylevel bandgap between the first and second compounds is more than 0.5eV, and as a result, electrical properties of the OLEDs were furtherdeteriorated and color purity of the OLEDs was decreased as the FWHM ofthe OLEDs is wide. On the other hand, holes were not trapped andexciplex was not formed in the OLEDs fabricated in Examples each ofwhich is designed to have the HOMO energy level bandgap between thefirst and second compounds is less than 0.3 eV.

In addition, compared to the OLEDs fabricated in Comparative Examples,the OLED fabricated in Examples decreased its driving voltage up to41.8%, and improved its current efficiency, power efficiency and EQE upto 479.4%, 453.0% and 229.0%, respectively.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the OLED and the organiclight emitting device including the OLED of the present disclosurewithout departing from the technical idea or scope of the disclosure.Thus, it is intended that the present disclosure cover the modificationsand variations of this disclosure provided they come within the scope ofthe appended claims and their equivalents.

What is claimed is:
 1. An organic light emitting diode, comprising: afirst electrode; a second electrode facing the first electrode; and anemissive layer disposed between the first and second electrodes andincluding at least one emitting material layer, wherein the at least oneemitting material layer includes a first compound and a second compound,and wherein the first compound has the following structure of Formula 1and the second compound has the following structure of Formula 4:

wherein each of X₁ to X₈ is independently CR₁ or N, wherein one of X₁ toX₄ is N and the rest of X₁ to X₄ is CR₁ and one of X₅ to X₈ is N and therest of X₅ to X₈ is CR₁, and R₁ is selected from the group consisting ofprotium, deuterium, tritium, a halogen atom, an unsubstituted orsubstituted silyl group, an unsubstituted or substituted C₁-C₂₀ alkylgroup, an unsubstituted or substituted C₁-C₂₀ alkyl amino group, anunsubstituted or substituted C₆-C₃₀ aromatic group and an unsubstitutedor substituted C₃-C₃₀ hetero aromatic group, wherein at least one of R₁is an unsubstituted or substituted C₁₀-C₃₀ hetero aromatic group havingat least one nitrogen atom;

wherein each of R₂₁ to R₂₄ is independently selected from the groupconsisting of protium, deuterium, tritium, boryl, amino, anunsubstituted or substituted C₁-C₂₀ alkyl group, an unsubstituted orsubstituted C₁-C₂₀ alkyl amino group, an unsubstituted or substitutedC₆-C₃₀ aromatic group and an unsubstituted or substituted C₃-C₃₀ heteroaromatic group, or adjacent two of R₂₁ to R₂₄ form an unsubstituted orsubstituted fused ring having boron and nitrogen, or an unsubstituted orsubstituted fused ring having sulfur; each of R₂₅ to R₂₈ isindependently selected from the group consisting of protium, deuterium,tritium, boryl, an unsubstituted or substituted C₁-C₂₀ alkyl group, anunsubstituted or substituted C₁-C₂₀ alkyl amino group, an unsubstitutedor substituted C₆-C₃₀ aromatic group and an unsubstituted or substitutedC₃-C₃₀ hetero aromatic group.
 2. The organic light emitting diode ofclaim 1, wherein a Highest Occupied Molecular Orbital (HOMO) energylevel of the first compound and a HOMO energy level of the secondcompound satisfy the following relationship in Equation (1):|HOMO^(FD)−HOMO^(DF)|<0.3 eV  (1). wherein HOMO^(FD) is a HOMO energylevel of the second compound and HOMO^(DF) is a HOMO energy level of thefirst compound.
 3. The organic light emitting diode of claim 1, whereinan energy level bandgap between a Highest Occupied Molecular Orbital(HOMO) energy level and a Lowest Unoccupied Molecular Orbital (LUMO)energy level of the first compound is between about 2.6 eV and about 3.1eV.
 4. The organic light emitting diode of claim 1, wherein the firstcompound has the following structure of Formula 2:

wherein one of Y₁ and Y₂ is CR₁₅ and the other of Y₁ and Y₂ is N; one ofY₃ and Y₄ is CR₁₆ and the other of Y₃ and Y₄ is N; each of Ru to R₁₆ isindependently selected from the group consisting of protium, deuterium,tritium, a halogen atom, an unsubstituted or substituted silyl group, anunsubstituted or substituted C₁-C₂₀ alkyl group, an unsubstituted orsubstituted C₁-C₂₀ alkyl amino group, an unsubstituted or substitutedC₆-C₃₀ aromatic group and an unsubstituted or substituted C₃-C₃₀ heteroaromatic group, and wherein at least one of R₁₁ to R₁₆ is selected fromthe group consisting of an unsubstituted or substituted carbazolylmoiety, an unsubstituted or substituted acridinyl moiety, anunsubstituted or substituted acridonyl moiety, an unsubstituted orsubstituted phenazinyl moiety, an unsubstituted or substitutedphenoxazinyl moiety and an unsubstituted or substituted phenothiazinylmoiety.
 5. The organic light emitting diode of claim 1, wherein thefirst compound is selected from the following compounds:


6. The organic light emitting diode of claim 1, wherein the secondcompound has the following structure of Formula 5A or Formula 5B:

wherein each of R₂₅ to R₂₈ and each of R₃₁ to R₃₄ is independentlyselected from the group consisting of protium, deuterium, tritium,boryl, an unsubstituted or substituted C₁-C₂₀ alkyl group, anunsubstituted or substituted C₁-C₂₀ alkyl amino group, an unsubstitutedor substituted C₆-C₃₀ aromatic group and an unsubstituted or substitutedC₃-C₃₀ hetero aromatic group.
 7. The organic light emitting diode ofclaim 1, wherein the second compound is selected from the followingcompounds:


8. The organic light emitting diode of claim 1, wherein the at least oneemitting material layer has a mono-layered structure.
 9. The organiclight emitting diode of claim 8, wherein the at least one emittingmaterial layer further comprise a third compound.
 10. The organic lightemitting diode of claim 9, wherein a singlet exciton energy level of thethird compound is higher than a singlet exciton energy level of thefirst compound.
 11. The organic light emitting diode of claim 9, whereincontents of the first compound is between about 5 wt % and about 30 wt%, contents of the second compound is between about 0.1 wt % and about 5wt % and contents of the third compound is between about 65 wt % toabout 90 wt % in the at least one emitting material layer.
 12. Theorganic light emitting diode of claim 1, wherein the at least oneemitting material layer includes a first emitting material layerdisposed between the first and second electrodes and a second emittingmaterial layer disposed between the first electrode and the firstemitting material layer or between the first emitting material layer andthe second electrode, and wherein the first emitting material layerincludes the first compound and the second emitting material layerincludes the second compound.
 13. The organic light emitting diode ofclaim 12, wherein the first emitting material layer further comprises afourth compound and the second emitting material layer further comprisesa fifth compound.
 14. The organic light emitting diode of claim 13,wherein a singlet exciton energy level of the fourth compound is higherthan a singlet exciton energy level of the first compound.
 15. Theorganic light emitting diode of claim 13, wherein a singlet excitonenergy level of the fifth compound is higher than a singlet excitonenergy level of the second compound.
 16. The organic light emittingdiode of claim 12, wherein the at least one emitting material layerfurther comprises a third emitting material layer disposed oppositely tothe second emitting material layer with respect to the first emittingmaterial layer.
 17. The organic light emitting diode of claim 16,wherein the third emitting material layer includes the second compound.18. The organic light emitting diode of claim 1, wherein the emissivelayer includes a first emitting part disposed between the first andsecond electrodes, a second emitting part disposed between the firstemitting part and the second electrode and a charge generation layerdisposed between the first and second emitting parts, and wherein atleast one of the first and second emitting parts includes the at leastone emitting material layer.
 19. The organic light emitting diode ofclaim 1, wherein the second compound has the following structure:

wherein the definitions of R₂₁ to R₂₈ are the same as the definition inclaim
 1. 20. An organic light emitting device comprising: a substrate;and an organic light emitting diode of claim 1 over the substrate. 21.The organic light emitting device of claim 20, further comprises a thinfilm transistor disposed over the substrate and connected to the organiclight emitting diode.